300 lines
16 KiB
JSON
300 lines
16 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2024-49940",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2024-10-21T12:17:06.043Z",
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"datePublished": "2024-10-21T18:01:59.668Z",
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"dateUpdated": "2026-10-30T12:19:44.806Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-30T12:19:44.806Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: prevent possible tunnel refcount underflow\n\nWhen a session is created, it sets a backpointer to its tunnel. When\nthe session refcount drops to 0, l2tp_session_free drops the tunnel\nrefcount if session->tunnel is non-NULL. However, session->tunnel is\nset in l2tp_session_create, before the tunnel refcount is incremented\nby l2tp_session_register, which leaves a small window where\nsession->tunnel is non-NULL when the tunnel refcount hasn't been\nbumped.\n\nMoving the assignment to l2tp_session_register is trivial but\nl2tp_session_create calls l2tp_session_set_header_len which uses\nsession->tunnel to get the tunnel's encap. Add an encap arg to\nl2tp_session_set_header_len to avoid using session->tunnel.\n\nIf l2tpv3 sessions have colliding IDs, it is possible for\nl2tp_v3_session_get to race with l2tp_session_register and fetch a\nsession which doesn't yet have session->tunnel set. Add a check for\nthis case."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The refcount underflow is triggered by local session creation — either the L2TP generic-netlink `L2TP_CMD_SESSION_CREATE` command or a `connect()` on an `AF_PPPOX`/`PX_PROTO_OL2TP` socket. A remote peer cannot itself drive `l2tp_session_create()`/`l2tp_session_register()`, though remote packets in `l2tp_udp_encap_recv()` are what subsequently dereference the prematurely freed tunnel.\nAC:L - The attacker fully controls both sides: they choose the session ID, so they can deterministically force `l2tp_session_register()` to fail (`-EEXIST` on a colliding L2TPv3 ID, or `-ENODEV`), and they can run concurrent create/teardown threads to widen the window between `l2tp_session_create()` and the tunnel refcount bump. No condition outside attacker influence is required, and L2TP is a stock distro module.\nPR:L - `pppol2tp_create()`/`pppox_create()` perform no capability check, so a plain unprivileged local user can reach `l2tp_session_create()` and `l2tp_session_register()` through `connect()`. The netlink path is `GENL_UNS_ADMIN_PERM` (CAP_NET_ADMIN against the netns user_ns), which any unprivileged user obtains via `unshare -Urn`.\nUI:N - The attacker performs the entire sequence — tunnel setup, session creation with a colliding ID, and session teardown — from their own process. No victim action or cooperating user is involved.\nS:U - The underflow and the resulting use-after-free are confined to the kernel's own l2tp objects within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The dropped-too-early tunnel reference frees `struct l2tp_tunnel` while `session->tunnel` and the datapath still reference it, giving a use-after-free on a kmalloc'd object that can be reclaimed with attacker-sprayed data and then read back (e.g. `tunnel->sock`, `tunnel->encap`, `tunnel->version` used in `l2tp_recv_common()`/`l2tp_xmit_skb()`), enabling kernel memory disclosure.\nI:H - A use-after-free on the tunnel object lets an attacker reoccupy the freed slab and control fields such as `tunnel->sock`, which the transmit and receive paths dereference and pass to socket operations, yielding a write/control-flow-hijack primitive. Additionally the extra `l2tp_tunnel_dec_refcount()` corrupts kernel reference-counting state itself.\nA:H - Premature tunnel free reliably produces an oops/panic when the still-live session or a received L2TP packet dereferences the dangling `session->tunnel`, and the `refcount_t` underflow itself raises a WARN that panics on `panic_on_warn` systems."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"net/l2tp/l2tp_core.c",
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"net/l2tp/l2tp_core.h",
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"net/l2tp/l2tp_netlink.c",
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"net/l2tp/l2tp_ppp.c"
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],
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"versions": [
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{
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"version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
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"lessThan": "aa7132362e79abc4f2add4d8657dd1679341edc5",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
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"lessThan": "98691b2e28a6c3dac0680914493d54c77f215755",
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"status": "affected",
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},
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{
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"version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
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"lessThan": "f7415e60c25a6108cd7955a20b2e66b6251ffe02",
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"status": "affected",
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{
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"lessThan": "24256415d18695b46da06c93135f5b51c548b950",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "b102bfc2a90d14f342580285782a9a51c74f7369",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "10c15ddabbcf888922adbdd44ca3fecf6eab19d9",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "8d1c650d452c53fcb3f02a7b1d772741639f89a4",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "12b5fb58ac993c24210cf8cbc72d407d3a4e6490",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "aef37401b467a0b1a9517c69924a1d66937e0789",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "3.2.99",
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"lessThan": "3.3",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "3.16.54",
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"lessThan": "3.17",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "4.4.225",
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"lessThan": "4.5",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "4.9.225",
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"lessThan": "4.10",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "4.14.182",
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"lessThan": "4.15",
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"status": "affected",
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"versionType": "semver"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"net/l2tp/l2tp_core.c",
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"net/l2tp/l2tp_core.h",
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"net/l2tp/l2tp_netlink.c",
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"net/l2tp/l2tp_ppp.c"
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],
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"versions": [
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{
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"version": "4.15",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "4.15",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.1.191",
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"lessThanOrEqual": "6.1.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.6.160",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.11.3",
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"lessThanOrEqual": "6.11.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.12",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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"cpeApplicability": [
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"operator": "OR",
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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{
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/aa7132362e79abc4f2add4d8657dd1679341edc5"
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},
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{
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"url": "https://git.kernel.org/stable/c/98691b2e28a6c3dac0680914493d54c77f215755"
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},
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{
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"url": "https://git.kernel.org/stable/c/f7415e60c25a6108cd7955a20b2e66b6251ffe02"
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},
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{
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"url": "https://git.kernel.org/stable/c/24256415d18695b46da06c93135f5b51c548b950"
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}
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],
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"title": "l2tp: prevent possible tunnel refcount underflow",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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},
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"adp": [
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{
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"metrics": [
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{
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"other": {
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"type": "ssvc",
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"content": {
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"id": "CVE-2024-49940",
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"role": "CISA Coordinator",
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"options": [
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{
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"Exploitation": "none"
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},
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{
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"Automatable": "no"
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},
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{
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"Technical Impact": "partial"
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}
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],
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"version": "2.0.3",
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"timestamp": "2024-10-22T13:37:52.827630Z"
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}
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}
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}
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],
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"title": "CISA ADP Vulnrichment",
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"providerMetadata": {
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"shortName": "CISA-ADP",
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"dateUpdated": "2024-10-22T13:38:50.656Z"
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}
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}
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]
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}
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} |