Use-After-Free in Linux kernel (CVE-2025-38554)
Summary
Vulnerability in Linux kernel (CVE-2025-38554). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
mm: fix a UAF when vma->mm is freed after vma->vm_refcnt got dropped
By inducing delays in the right places, Jann Horn created a reproducer for
a hard to hit UAF issue that became possible after VMAs were allowed to be
recycled by adding SLAB_TYPESAFE_BY_RCU to their cache.
Race description is borrowed from Jann's discovery report:
lock_vma_under_rcu() looks up a VMA locklessly with mas_walk() under
rcu_read_lock(). At that point, the VMA may be concurrently freed, and it
can be recycled by another process. vma_start_read() then increments the
vma->vm_refcnt (if it is in an acceptable range), and if this succeeds,
vma_start_read() can return a recycled VMA.
In this scenario where the VMA has been recycled, lock_vma_under_rcu()
will then detect the mismatching ->vm_mm pointer and drop the VMA through
vma_end_read(), which calls vma_refcount_put(). vma_refcount_put() drops
the refcount and then calls rcuwait_wake_up() using a copy of vma->vm_mm.
This is wrong: It implicitly assumes that the caller is keeping the VMA's
mm alive, but in this scenario the caller has no relation to the VMA's mm,
so the rcuwait_wake_up() can cause UAF.
The diagram depicting the race:
T1 T2 T3
== == ==
lock_vma_under_rcu
mas_walk
mmap
vma_start_read
__refcount_inc_not_zero_limited_acquire
munmap…
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2025-38554 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2025-38554" on the vendor's site.
CVE-2025-38554 (Linux kernel) — CWE-416 / CVSS v3 7.8
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Use-after-free (CWE-416) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2025-38554 linux-lts Fixed in: 6.18.35-r1
- Ubuntu UBUNTU-CVE-2025-38554 linux-hwe-edge
References
- advisory github.com
- advisory nvd.nist.gov
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org