CVE-2026-64581 (GCVE-0-2026-64581)
Vulnerability from cvelistv5
Published
2026-08-05 08:09
Modified
2026-08-27 12:39
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
xfrm: fix sk_dst_cache double-free in xfrm_user_policy()
xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(),
i.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with
rcu_dereference_protected(), stores NULL and dst_release()s the old dst.
That is only safe if no other thread modifies sk_dst_cache concurrently.
For a connected UDP socket that does not hold: the transmit fast path
(udp_sendmsg -> sk_dst_check -> sk_dst_reset) resets the cache locklessly
with an atomic xchg(). A per-socket policy change racing a send can make
both sides observe the same old dst and each dst_release() it, dropping
the socket's single reference twice and freeing the xfrm_dst bundle while
it is still referenced:
BUG: KASAN: slab-use-after-free in dst_release
Write of size 4 at addr ffff88801897b6c0 by task exploit/155
Call Trace:
...
dst_release (... ./include/linux/rcuref.h:109)
xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053)
do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347)
ip_setsockopt (net/ipv4/ip_sockglue.c:1417)
do_sock_setsockopt (net/socket.c:2368)
__sys_setsockopt (net/socket.c:2393)
__x64_sys_setsockopt (net/socket.c:2396)
do_syscall_64 (arch/x86/entry/syscall_64.c:94)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
Reachable by an unprivileged user via a user+network namespace.
Use the atomic sk_dst_reset() so the cache is cleared and released with a
single xchg(): whichever side wins releases the dst once, the other sees
NULL and does nothing. Behaviour is otherwise unchanged.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 Version: 72f157be2f81910ae759bfe2e5c2256fc4625645 Version: 9e9fe58a92a46c6d154d2901735bf230d91b8507 Version: adc1ec6cdc20d430aa01b86497220709b9149466 Version: b54033eb1cfd77aba471269ddd804ed8d3e35dea Version: c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a Version: 5eef9b51114fcc65651d671add52f267f91b9451 Version: 3.16.52 ≤ Version: 4.4.163 ≤ Version: 3.18.101 ≤ Version: 4.1.52 ≤ Version: 4.4.123 ≤ Version: 4.9.89 ≤ |
||
{
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}
]
}
],
"cpeApplicability": [
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"nodes": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: fix sk_dst_cache double-free in xfrm_user_policy()\n\nxfrm_user_policy() clears the socket dst cache with __sk_dst_reset(),\ni.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with\nrcu_dereference_protected(), stores NULL and dst_release()s the old dst.\nThat is only safe if no other thread modifies sk_dst_cache concurrently.\n\nFor a connected UDP socket that does not hold: the transmit fast path\n(udp_sendmsg -\u003e sk_dst_check -\u003e sk_dst_reset) resets the cache locklessly\nwith an atomic xchg(). A per-socket policy change racing a send can make\nboth sides observe the same old dst and each dst_release() it, dropping\nthe socket\u0027s single reference twice and freeing the xfrm_dst bundle while\nit is still referenced:\n\n BUG: KASAN: slab-use-after-free in dst_release\n Write of size 4 at addr ffff88801897b6c0 by task exploit/155\n Call Trace:\n ...\n dst_release (... ./include/linux/rcuref.h:109)\n xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053)\n do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347)\n ip_setsockopt (net/ipv4/ip_sockglue.c:1417)\n do_sock_setsockopt (net/socket.c:2368)\n __sys_setsockopt (net/socket.c:2393)\n __x64_sys_setsockopt (net/socket.c:2396)\n do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n\nReachable by an unprivileged user via a user+network namespace.\n\nUse the atomic sk_dst_reset() so the cache is cleared and released with a\nsingle xchg(): whichever side wins releases the dst once, the other sees\nNULL and does nothing. Behaviour is otherwise unchanged."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - Triggered via setsockopt(IP_XFRM_POLICY/IP_IPSEC_POLICY) on a local socket racing concurrent udp_sendmsg; entry is a local syscall path (do_ip_setsockopt -\u003e xfrm_user_policy), not packet processing.\nAC:L - Attacker controls both sides of the race (one thread setsockopt to clear/apply per-socket xfrm policy, another sendmsg on the same connected UDP socket) and can create the obsolete xfrm_dst precondition in their netns, retrying until the double dst_release wins.\nPR:L - Path requires CAP_NET_ADMIN checked with sockopt_ns_capable(sock_net(sk)-\u003euser_ns), which an unprivileged user obtains via user+network namespaces; the fix commit explicitly states this reachability.\nUI:N - Exploitation uses only the attacker\u0027s own socket, threads, and setsockopt/sendmsg loops; no victim action or cooperation is required.\nS:U - Double-free/UAF of the socket\u0027s dst_entry/xfrm_dst is standard local kernel memory corruption within the host kernel authority, not a VM escape or other cross-boundary impact.\nC:H - Double dst_release frees the xfrm_dst slab object while still referenced, yielding a use-after-free that can be reclaimed/sprayed to disclose kernel memory via corrupted dst contents and ops.\nI:H - The UAF targets a dst_entry with function pointers (ops/input/output) used on transmit, enabling heap reuse for arbitrary write and control-flow hijack consistent with comparable sk_dst_cache races.\nA:H - The KASAN slab-use-after-free in dst_release demonstrates kernel memory corruption that can oops/panic, and the attacker can repeat the race freely."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-27T12:39:44.254Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/e8686fd8d18b99f3a9038683045b2f2338a7706d"
},
{
"url": "https://git.kernel.org/stable/c/a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9"
},
{
"url": "https://git.kernel.org/stable/c/f833821e4b52ab6335d443ede5fb79c38e61d19a"
},
{
"url": "https://git.kernel.org/stable/c/f0ab9a71167bae308e05ab13b65e2007504a603f"
},
{
"url": "https://git.kernel.org/stable/c/8dd8929b71c4f06c614f8f54c2cc070453faae16"
},
{
"url": "https://git.kernel.org/stable/c/0ea8f06454012d9e7f9c6e6253df710949bf6294"
},
{
"url": "https://git.kernel.org/stable/c/96b678d08268b5f5c6fc99d4289d9b7e334fc683"
},
{
"url": "https://git.kernel.org/stable/c/c283e9ada7fcb7dd4b10592623086b2e6d2f9925"
}
],
"title": "xfrm: fix sk_dst_cache double-free in xfrm_user_policy()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-64581",
"datePublished": "2026-08-05T08:09:35.556Z",
"dateReserved": "2026-07-19T15:36:31.798Z",
"dateUpdated": "2026-08-27T12:39:44.254Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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