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vuln-cve/data/2026/63xxx/CVE-2026-63803.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-63803",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2026-07-19T07:54:57.013Z",
"datePublished": "2026-07-19T12:02:08.574Z",
"dateUpdated": "2026-10-19T20:07:47.971Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-08-17T04:51:08.890Z"
},
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nhdlc_ppp: sync per-proto timers before freeing hdlc state\n\nEach PPP control protocol (LCP/IPCP/IPV6CP) embedded in struct ppp\nregisters a timer via timer_setup(). That struct ppp is the\nhdlc->state allocation, which detach_hdlc_protocol() frees with kfree()\nin both teardown paths: unregister_hdlc_device() and the re-attach inside\nattach_hdlc_protocol().\n\nThe ppp proto never registered a .detach callback, so\ndetach_hdlc_protocol() performs no timer synchronization before the\nkfree(). The only cancel, timer_delete(&proto->timer) in ppp_cp_event(),\nis partial (it does not wait for a running callback) and only runs on the\n->CLOSED transition; ppp_stop()/ppp_close() do not sync either. A\nppp_timer callback already executing (blocked on ppp->lock) survives the\nkfree and then dereferences proto->state / ppp->lock in freed memory,\nleading to a use-after-free.\n\nFix this by adding a .detach helper that calls timer_shutdown_sync() on\nevery per-proto timer. detach_hdlc_protocol() invokes proto->detach(dev)\nbefore kfree(hdlc->state), so timer_shutdown_sync()\nnow runs on both free paths.\ntimer_shutdown_sync() is used instead of timer_delete_sync() because the\nkeepalive path re-arms the timer through add_timer()/mod_timer() and\nshutdown blocks any re-activation during teardown.\n\nInitialize the per-protocol timers in ppp_ioctl() when the protocol is\nattached, and remove the now-redundant timer_setup() from ppp_start(), so\nthat the timers are initialized exactly once at attach time and\nppp_timer_release() never operates on uninitialized timer_list\nstructures. attach_hdlc_protocol() uses kmalloc() (not kzalloc), so\nstruct ppp's protos[i].timer is uninitialized garbage until the first\ntimer_setup(); without this init-at-attach, attaching the PPP protocol\nwithout ever bringing the device up would leave timer_shutdown_sync()\noperating on uninitialized memory in .detach. Moving the init out of\nppp_start() (which only runs on NETDEV_UP) into the attach path makes the\ninitialization unconditional and avoids initializing the same timer_list\ntwice.\n\nThis bug was found by static analysis."
}
],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"baseScore": 7.8,
"baseSeverity": "HIGH"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The UAF occurs in detach_hdlc_protocol() during protocol teardown via SIOCWANDEV ioctl or driver unregister, not during packet receive. Remote PPP peers can influence timers but cannot reach the kfree() path without local CAP_NET_ADMIN configuration actions.\nAC:L - An attacker with CAP_NET_ADMIN can reliably trigger the bug by bringing a PPP HDLC interface up (arming timers via ppp_start/LCP), then tearing down or re-attaching the protocol while timers are pending or a ppp_timer callback is blocked on ppp->lock, controlling both sides of the race.\nPR:L - Exploitation requires CAP_NET_ADMIN to attach/detach the PPP protocol via SIOCWANDEV (ppp_ioctl checks capable(CAP_NET_ADMIN)), which is reachable by unprivileged users who create user namespaces with CAP_NET_ADMIN per kernel CVSS guidance.\nUI:N - No victim interaction is required once the attacker has network administration capability on a system with an HDLC WAN device; exploitation is fully attacker-driven through ioctl and interface up/down operations.\nS:U - The use-after-free corrupts kernel heap memory within the same kernel security boundary, enabling local privilege escalation rather than crossing a VM, container, or IOMMU security boundary.\nC:H - Use-after-free of struct ppp and its embedded spinlock_t allows dereferencing attacker-influenced freed heap memory, which can be leveraged for arbitrary kernel memory read via heap grooming and controlled reuse of the freed slab object.\nI:H - The UAF on struct ppp and ppp->lock provides a standard kernel heap corruption primitive that can be developed into arbitrary write and local privilege escalation through control of reallocated object contents and spinlock corruption.\nA:H - The freed-memory dereference in ppp_timer() causes kernel oops or panic during protocol teardown, and repeated triggering during interface reconfiguration can cause sustained denial of service on WAN router systems."
}
]
}
],
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{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"drivers/net/wan/hdlc_ppp.c"
],
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"status": "affected",
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{
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"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
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],
"versions": [
{
"version": "2.6.12",
"status": "affected"
},
{
"version": "0",
"lessThan": "2.6.12",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.10.261",
"lessThanOrEqual": "5.10.*",
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{
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},
{
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"status": "unaffected",
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},
{
"version": "7.1.3",
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},
{
"version": "7.2",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
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"nodes": [
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"operator": "OR",
"negate": false,
"cpeMatch": [
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"references": [
{
"url": "https://git.kernel.org/stable/c/86d80a231bde4cfb64bfbfbfffd83056fc93628f"
},
{
"url": "https://git.kernel.org/stable/c/8308122bc9c065b1f376e081ed300129a2ac9545"
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{
"url": "https://git.kernel.org/stable/c/ce8f9ddca0c9f217342a8b49efd309aa35b81a36"
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},
{
"url": "https://git.kernel.org/stable/c/c78a4e41ab5ead6193ad8a2dd92e8906bae659fa"
}
],
"title": "hdlc_ppp: sync per-proto timers before freeing hdlc state",
"x_generator": {
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}
},
"adp": [
{
"metrics": [
{
"other": {
"type": "ssvc",
"content": {
"id": "CVE-2026-63803",
"role": "CISA Coordinator",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"version": "2.0.3",
"timestamp": "2026-10-16T15:30:49.056800Z"
}
}
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"type": "CWE",
"cweId": "CWE-416",
"description": "CWE-416 Use After Free"
}
]
}
],
"title": "CISA ADP Vulnrichment",
"providerMetadata": {
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP",
"dateUpdated": "2026-10-19T20:07:47.971Z"
}
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]
}
}