227 lines
12 KiB
JSON
227 lines
12 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-2020-36791",
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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": "2024-02-26T17:07:27.435Z",
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"datePublished": "2025-05-07T13:17:33.882Z",
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"dateUpdated": "2026-08-05T08:44:33.087Z"
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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": "2026-08-05T08:44:33.087Z"
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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\nnet_sched: keep alloc_hash updated after hash allocation\n\nIn commit 599be01ee567 (\"net_sched: fix an OOB access in cls_tcindex\")\nI moved cp->hash calculation before the first\ntcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched.\nThis difference could lead to another out of bound access.\n\ncp->alloc_hash should always be the size allocated, we should\nupdate it after this tcindex_alloc_perfect_hash()."
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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 bug is triggered through the tc filter netlink configuration path (RTM_NEWTFILTER → tc_new_tfilter → tcindex_change → tcindex_set_parms), not by processing network packets. Exploitation requires local netlink/syscall access to configure cls_tcindex.\nAC:L - An attacker fully controls both the old and new hash sizes and the filter handle via netlink attributes, so shrinking a perfect hash while using a handle past the newly allocated size reliably produces the OOB access with no race or external conditions.\nPR:L - tc_new_tfilter requires CAP_NET_ADMIN checked with netlink_ns_capable against the network namespace's user_ns, which an unprivileged user can obtain via user namespaces (unshare -Urn) without real root in the init namespace.\nUI:N - The attacker creates and modifies their own tcindex filters in a network namespace they control; no victim action is required.\nS:U - Impact is confined to the host kernel privilege boundary (local memory corruption / privilege escalation) and does not cross VM, IOMMU, or other distinct security authorities.\nC:H - Stale alloc_hash allows OOB reads through tcindex_get/tcindex_lookup (perfect + handle beyond the allocated array), and the heap OOB can be leveraged for arbitrary kernel memory disclosure.\nI:H - tcindex_set_parms does r = cp->perfect + handle then writes result/exts into that slot; with handle past the newly allocated hash this is a controlled heap out-of-bounds write enabling memory corruption and control-flow hijacking.\nA:H - The out-of-bounds access was caught by syzbot as a kernel memory-safety failure and can produce oops/panic or heap corruption leading to a crash even without full exploitation."
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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/sched/cls_tcindex.c"
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],
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"versions": [
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"version": "73c29d2f6f8ae731b1e09051b69ed3ba2319482b",
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"lessThan": "d6cdc5bb19b595486fb2e6661e5138d73a57f454",
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"status": "affected",
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"status": "affected",
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"version": "dd8142a6fa5270783d415292ec8169f4ea2a5468",
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"lessThan": "d23faf32e577922b6da20bf3740625c1105381bf",
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"status": "affected",
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"versionType": "git"
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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": "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/sched/cls_tcindex.c"
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],
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"versions": [
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{
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"version": "4.4.214",
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"lessThan": "4.4.218",
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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": "4.9.214",
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"lessThan": "4.9.218",
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"status": "affected",
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},
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{
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"version": "4.14.171",
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"lessThan": "4.14.175",
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"status": "affected",
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},
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{
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"version": "4.19.103",
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"lessThan": "4.19.114",
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"status": "affected",
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},
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{
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"version": "5.4.19",
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"lessThan": "5.4.29",
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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": "5.5.3",
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"lessThan": "5.5.14",
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"status": "affected",
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"references": [
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"url": "https://git.kernel.org/stable/c/d6cdc5bb19b595486fb2e6661e5138d73a57f454"
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"url": "https://git.kernel.org/stable/c/d23faf32e577922b6da20bf3740625c1105381bf"
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{
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"url": "https://git.kernel.org/stable/c/bd3ee8fb6371b45c71c9345cc359b94da2ddefa9"
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},
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{
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"url": "https://git.kernel.org/stable/c/0d1c3530e1bd38382edef72591b78e877e0edcd3"
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},
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{
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"url": "https://syzkaller.appspot.com/bug?id=ea260693da894e7b078d18fca2c9c0a19b457534"
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},
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{
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"url": "https://blog.cdthoughts.ch/2021/03/16/syzbot-bug.html"
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}
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],
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"title": "net_sched: keep alloc_hash updated after hash allocation",
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