CVE-2026-64581 (GCVE-0-2026-64581)

Vulnerability from cvelistv5 – Published: 2026-08-05 08:09 – Updated: 2026-08-08 15:13
VLAI
Title
xfrm: fix sk_dst_cache double-free in xfrm_user_policy()
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.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 , < 96b678d08268b5f5c6fc99d4289d9b7e334fc683 (git)
Affected: 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 , < c283e9ada7fcb7dd4b10592623086b2e6d2f9925 (git)
Affected: 72f157be2f81910ae759bfe2e5c2256fc4625645 (git)
Affected: 9e9fe58a92a46c6d154d2901735bf230d91b8507 (git)
Affected: adc1ec6cdc20d430aa01b86497220709b9149466 (git)
Affected: b54033eb1cfd77aba471269ddd804ed8d3e35dea (git)
Affected: c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a (git)
Affected: 5eef9b51114fcc65651d671add52f267f91b9451 (git)
Affected: 3.16.52 , < 3.17 (semver)
Affected: 4.4.163 , < 4.5 (semver)
Affected: 3.18.101 , < 3.19 (semver)
Affected: 4.1.52 , < 4.2 (semver)
Affected: 4.4.123 , < 4.5 (semver)
Affected: 4.9.89 , < 4.10 (semver)
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Linux Linux Affected: 4.14
Unaffected: 0 , < 4.14 (semver)
Unaffected: 7.1.6 , ≤ 7.1.* (semver)
Unaffected: 7.2-rc4 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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{
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          "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."
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            "version": "3.1"
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              "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."
            }
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        "dateUpdated": "2026-08-08T15:13:18.261Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "title": "xfrm: fix sk_dst_cache double-free in xfrm_user_policy()",
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    "dateReserved": "2026-07-19T15:36:31.798Z",
    "dateUpdated": "2026-08-08T15:13:18.261Z",
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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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/xfrm/xfrm_state.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"2b06cdf3e688b98fcc9945873b5d42792bd4eee0\",\"lessThan\":\"96b678d08268b5f5c6fc99d4289d9b7e334fc683\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"2b06cdf3e688b98fcc9945873b5d42792bd4eee0\",\"lessThan\":\"c283e9ada7fcb7dd4b10592623086b2e6d2f9925\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"72f157be2f81910ae759bfe2e5c2256fc4625645\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"9e9fe58a92a46c6d154d2901735bf230d91b8507\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"adc1ec6cdc20d430aa01b86497220709b9149466\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"b54033eb1cfd77aba471269ddd804ed8d3e35dea\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5eef9b51114fcc65651d671add52f267f91b9451\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"3.16.52\",\"lessThan\":\"3.17\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"4.4.163\",\"lessThan\":\"4.5\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"3.18.101\",\"lessThan\":\"3.19\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"4.1.52\",\"lessThan\":\"4.2\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"4.4.123\",\"lessThan\":\"4.5\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"4.9.89\",\"lessThan\":\"4.10\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/xfrm/xfrm_state.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"4.14\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"4.14\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.6\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2-rc4\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/96b678d08268b5f5c6fc99d4289d9b7e334fc683\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c283e9ada7fcb7dd4b10592623086b2e6d2f9925\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.