# CVE-2026-53239: xfrm: policy: fix use-after-free on inexact bin in xfrm_policy_bysel_ctx()

Status: published. Published: 2026-06-25. Updated: 2026-11-10.

In the Linux kernel, the following vulnerability has been resolved:

xfrm: policy: fix use-after-free on inexact bin in xfrm_policy_bysel_ctx()

Fix the race by pruning the bin while still holding xfrm_policy_lock,
before dropping it. Use __xfrm_policy_inexact_prune_bin() directly since
the lock is already held. The wrapper xfrm_policy_inexact_prune_bin()
becomes unused and is removed.

Race:

  CPU0 (XFRM_MSG_DELPOLICY)           CPU1 (XFRM_MSG_NEWSPDINFO)
  ==========================          ==========================
  xfrm_policy_bysel_ctx():
    spin_lock_bh(xfrm_policy_lock)
    bin = xfrm_policy_inexact_lookup()
    __xfrm_policy_unlink(pol)
    spin_unlock_bh(xfrm_policy_lock)
    xfrm_policy_kill(ret)
    // wide window, lock not held
                                       xfrm_hash_rebuild():
                                         spin_lock_bh(xfrm_policy_lock)
                                         __xfrm_policy_inexact_flush():
                                           kfree_rcu(bin)  // bin freed
                                         spin_unlock_bh(xfrm_policy_lock)
    xfrm_policy_inexact_prune_bin(bin)
    // UAF: bin is freed

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < 8fc536e9f6856230f19c7d13e71af064b6a77b22 (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < c4c1ea36d83bf3c4569468ca5b8b614fda1bf821 (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < 25c8c7fb3b0b9668c7d05e209f58c158d2b020c7 (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < 42827d03f8009a6a218bacab153e21f39d6a121c (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < 88697cf980222d5906a37bf47662dac0732e2a0f (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < b5316e2b8614a87d8736941972441cb47bfd4491 (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < ec82ea4eb220164d854f8734ca5a35e23e577b94 (affected, git); ≥ 6be3b0db6db82cf056a72cc18042048edd27f8ee; < 7f2d76c9c03257c0782afef9d95321fa04096f60 (affected, git). Source: CNA: Linux
- Linux / Linux: 5.0 (affected); ≥ 0; < 5.0 (unaffected, semver); ≥ 5.10.259; ≤ 5.10.* (unaffected, semver); ≥ 5.15.210; ≤ 5.15.* (unaffected, semver); ≥ 6.1.176; ≤ 6.1.* (unaffected, semver); ≥ 6.6.143; ≤ 6.6.* (unaffected, semver); ≥ 6.12.94; ≤ 6.12.* (unaffected, semver); ≥ 6.18.36; ≤ 6.18.* (unaffected, semver); ≥ 7.0.13; ≤ 7.0.* (unaffected, semver); ≥ 7.1; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 TM MFP - GNU/Linux subsystem: ≥ 0; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.6; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: Linux

- CISA KEV: No listing in collected sources

- EPSS: 0.10% as of 2026-11-09; percentile 0.92%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-362

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/8fc536e9f6856230f19c7d13e71af064b6a77b22 (CNA: Linux)

- https://git.kernel.org/stable/c/c4c1ea36d83bf3c4569468ca5b8b614fda1bf821 (CNA: Linux)

- https://git.kernel.org/stable/c/25c8c7fb3b0b9668c7d05e209f58c158d2b020c7 (CNA: Linux)

- https://git.kernel.org/stable/c/42827d03f8009a6a218bacab153e21f39d6a121c (CNA: Linux)

- https://git.kernel.org/stable/c/88697cf980222d5906a37bf47662dac0732e2a0f (CNA: Linux)

- https://git.kernel.org/stable/c/b5316e2b8614a87d8736941972441cb47bfd4491 (CNA: Linux)

- https://git.kernel.org/stable/c/ec82ea4eb220164d854f8734ca5a35e23e577b94 (CNA: Linux)

- https://git.kernel.org/stable/c/7f2d76c9c03257c0782afef9d95321fa04096f60 (CNA: Linux)

- https://cert-portal.siemens.com/productcert/html/ssa-019113.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

- https://cert-portal.siemens.com/productcert/html/ssa-784472.html (ADP: siemens-SADP)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-53239; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-53239; retrieved 2026-11-10; source updated Not reported

Revision: ef46d97ef882b3b88fbda21885cfb7de64128902e9674b94ee43b59b1f5426cb

Canonical: https://y2.dev/cve/CVE-2026-53239

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