CVE-2026-64581

Full vulnerability record from the local CVENow database.

Description

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

HIGH

CVSS score

7.8 (v3.1)

Vulnerability status

Received

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-08-05 08:16:38.177000

Last modified

2026-10-19 21:17:48.343000

View original CVE JSON

{
  "id": "CVE-2026-64581",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-08-05T08:16:38.177",
  "lastModified": "2026-10-19T21:17:48.343",
  "vulnStatus": "Received",
  "cveTags": [],
  "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 -> sk_dst_check -> 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's 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": "e8686fd8d18b99f3a9038683045b2f2338a7706d",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2b06cdf3e688b98fcc9945873b5d42792bd4eee0",
              "lessThan": "a9340ebdc13f8bb5063c0bc0b037ee7e640d4ae9",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2b06cdf3e688b98fcc9945873b5d42792bd4eee0",
              "lessThan": "f833821e4b52ab6335d443ede5fb79c38e61d19a",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "2b06cdf3e688b98fcc9945873b5d42792bd4eee0",
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              "versionType": "git",
              "status": "affected"
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              "versionType": "git",
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              "versionType": "git",
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              "versionType": "git",
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              "versionType": "git",
              "status": "affected"
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              "version": "adc1ec6cdc20d430aa01b86497220709b9149466",
              "versionType": "git",
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              "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": [
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              "version": "4.14",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "4.14",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.10.267",
              "lessThanOrEqual": "5.10.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "5.15.218",
              "lessThanOrEqual": "5.15.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.1.185",
              "lessThanOrEqual": "6.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.6.154",
              "lessThanOrEqual": "6.6.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.12.106",
              "lessThanOrEqual": "6.12.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.18.47",
              "lessThanOrEqual": "6.18.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.1.6",
              "lessThanOrEqual": "7.1.*",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "7.2",
              "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
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-10-16T15:43:16.753183Z",
          "id": "CVE-2026-64581",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-362"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/0ea8f06454012d9e7f9c6e6253df710949bf6294",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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}