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TI-2025-25688 Aliases CVE-2025-38349GHSA-c7h3-7f54-949m

eventpoll: don't decrement ep refcount while still holding the ep mutex

Priority LOW 35CWE-416Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 20 fixed, 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

In the Linux kernel, the following vulnerability has been resolved: eventpoll: don't decrement ep refcount while still holding the ep mutex Jann Horn points out that epoll is decrementing the ep refcount and then doing a mutex_unlock(&ep->mtx); afterwards. That's very wrong, because it can lead to a use-after-free. That pattern is actually fine for the very last reference, because the code in question will delay the actual call to "ep_free(ep)" until after it has unlocked the mutex. But it's wrong for the much subtler "next to last" case when somebody *else* may also be dropping their reference and free the ep while we're still using the mutex. Note that this is true even if that other user is also using the same ep mutex: mutexes, unlike spinlocks, can not be used for object ownership, even if they guarantee mutual exclusion. A mutex "unlock" operation is not atomic, and as one user is still accessing the mutex as part of unlocking it, another user can come in and get the now released mutex and free the data structure while the first user is still cleaning up. See our mutex documentation in Documentation/locking/mutex-design.rst, in particular the section [1] about semantics: "mutex_unlock() may access the mutex structure even after it has internally released the lock already - so it's not safe for another context to acquire the mutex and assume that the mutex_unlock() context is not using the structure anymore" So if we drop our ep ref before the mutex unlock, but we weren't the last one, we may then unlock the mutex, another user comes in, drops _their_ reference and releases the 'ep' as it now has no users - all while the mutex_unlock() is still accessing it. Fix this by simply moving the ep refcount dropping to outside the mutex: the refcount itself is atomic, and doesn't need mutex protection (that's the whole _point_ of refcounts: unlike mutexes, they are inherently about object lifetimes).

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00184 8th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.15.222, 6.1.178, 6.6.99 +3Red Hat: 4 advisoriesRed Hat: 20 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.15.209 to before 5.15.222; 6.1.175 to before 6.1.1785.15.222, 6.1.178Patch availableCNA
LinuxLinux6.4 and later5.15.222, 6.1.178, 6.6.99, 6.12.39, 6.15.7, 6.16Patch availableCNA
  • Linux VendorLinux Affected 5.15.209 to before 5.15.222; 6.1.175 to before 6.1.178 Fixed in 5.15.222, 6.1.178 Patch available CNA
  • Linux VendorLinux Affected 6.4 and later Fixed in 5.15.222, 6.1.178, 6.6.99, 6.12.39, 6.15.7, 6.16 Patch available CNA

CPE configurations NVD · 6

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*6.4 to before 6.6.99; 6.7 to before 6.12.39; 6.13 to before 6.15.7VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.16:rc1:*:*:*:*:*:*6.16 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.16:rc2:*:*:*:*:*:*6.16 rc2VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.16:rc3:*:*:*:*:*:*6.16 rc3VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.16:rc4:*:*:*:*:*:*6.16 rc4VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.16:rc5:*:*:*:*:*:*6.16 rc5VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 6.4 to before 6.6.99; 6.7 to before 6.12.39; 6.13 to before 6.15.7 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.16:rc1:*:*:*:*:*:* Versions 6.16 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.16:rc2:*:*:*:*:*:* Versions 6.16 rc2 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.16:rc3:*:*:*:*:*:* Versions 6.16 rc3 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.16:rc4:*:*:*:*:*:* Versions 6.16 rc4 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.16:rc5:*:*:*:*:*:* Versions 6.16 rc5 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.15.222, 6.1.178
  • Fix · CNA Linux (Linux) Fixed in 5.15.222, 6.1.178, 6.6.99, 6.12.39, 6.15.7, 6.16

Red Hat 4 advisories

  • RHSA-2026:4111 Released 2026-03-09 · Red Hat rating Moderate
    kernel security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) kernel-64k-debug-devel-6.12.0-55.63.1.el10_0, kernel-64k-debug-devel-matched-6.12.0-55.63.1.el10_0, kernel-64k-devel-6.12.0-55.63.1.el10_0 +12
    • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel-6.12.0-55.63.1.el10_0, kernel-64k-6.12.0-55.63.1.el10_0, kernel-64k-core-6.12.0-55.63.1.el10_0 +28
    • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) kernel-tools-libs-devel-6.12.0-55.63.1.el10_0, libperf-6.12.0-55.63.1.el10_0
    • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt-6.12.0-55.63.1.el10_0, kernel-rt-64k-6.12.0-55.63.1.el10_0, kernel-rt-64k-core-6.12.0-55.63.1.el10_0 +21
    • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt-6.12.0-55.63.1.el10_0, kernel-rt-core-6.12.0-55.63.1.el10_0, kernel-rt-debug-6.12.0-55.63.1.el10_0 +11
  • RHSA-2026:2759 Released 2026-02-16 · Red Hat rating Moderate
    kernel security update
    • Red Hat CodeReady Linux Builder EUS (v.9.6) kernel-tools-libs-devel-5.14.0-570.89.1.el9_6, libperf-5.14.0-570.89.1.el9_6
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) kernel-64k-debug-devel-5.14.0-570.89.1.el9_6, kernel-64k-debug-devel-matched-5.14.0-570.89.1.el9_6, kernel-64k-devel-5.14.0-570.89.1.el9_6 +12
    • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel-5.14.0-570.89.1.el9_6, kernel-64k-5.14.0-570.89.1.el9_6, kernel-64k-core-5.14.0-570.89.1.el9_6 +28
    • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt-5.14.0-570.89.1.el9_6, kernel-rt-64k-5.14.0-570.89.1.el9_6, kernel-rt-64k-core-5.14.0-570.89.1.el9_6 +21
    • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt-5.14.0-570.89.1.el9_6, kernel-rt-core-5.14.0-570.89.1.el9_6, kernel-rt-debug-5.14.0-570.89.1.el9_6 +11
  • RHSA-2026:1690 Released 2026-02-02 · Red Hat rating Important
    kernel security update
    • Red Hat Enterprise Linux AppStream (v. 10) kernel-64k-debug-devel-6.12.0-124.31.1.el10_1, kernel-64k-debug-devel-matched-6.12.0-124.31.1.el10_1, kernel-64k-devel-6.12.0-124.31.1.el10_1 +12
    • Red Hat Enterprise Linux BaseOS (v. 10) kernel-6.12.0-124.31.1.el10_1, kernel-64k-6.12.0-124.31.1.el10_1, kernel-64k-core-6.12.0-124.31.1.el10_1 +29
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) kernel-tools-libs-devel-6.12.0-124.31.1.el10_1, libperf-6.12.0-124.31.1.el10_1
    • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt-6.12.0-124.31.1.el10_1, kernel-rt-64k-6.12.0-124.31.1.el10_1, kernel-rt-64k-core-6.12.0-124.31.1.el10_1 +21
    • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt-6.12.0-124.31.1.el10_1, kernel-rt-core-6.12.0-124.31.1.el10_1, kernel-rt-debug-6.12.0-124.31.1.el10_1 +9
Show 1 more Red Hat advisories
  • RHSA-2026:1143 Released 2026-01-26 · Red Hat rating Important
    kernel security update
    • Red Hat Enterprise Linux AppStream (v. 9) kernel-64k-debug-devel-5.14.0-611.26.1.el9_7, kernel-64k-debug-devel-matched-5.14.0-611.26.1.el9_7, kernel-64k-devel-5.14.0-611.26.1.el9_7 +12
    • Red Hat Enterprise Linux BaseOS (v. 9) kernel-5.14.0-611.26.1.el9_7, kernel-64k-5.14.0-611.26.1.el9_7, kernel-64k-core-5.14.0-611.26.1.el9_7 +28
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) kernel-tools-libs-devel-5.14.0-611.26.1.el9_7, libperf-5.14.0-611.26.1.el9_7
    • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt-5.14.0-611.26.1.el9_7, kernel-rt-64k-5.14.0-611.26.1.el9_7, kernel-rt-64k-core-5.14.0-611.26.1.el9_7 +21
    • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt-5.14.0-611.26.1.el9_7, kernel-rt-core-5.14.0-611.26.1.el9_7, kernel-rt-debug-5.14.0-611.26.1.el9_7 +9

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 7AffectedNo fix yet
Red Hat Enterprise Linux 8AffectedNo fix yet
Red Hat Enterprise Linux 9AffectedNo fix yet
Red Hat CodeReady Linux Builder EUS (v.9.6)Fixed RHSA-2026:2759
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:1690
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:1143
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:4111
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:2759
Red Hat Enterprise Linux BaseOS (v. 10)Fixed RHSA-2026:1690
Red Hat Enterprise Linux BaseOS (v. 9)Fixed RHSA-2026:1143
Red Hat Enterprise Linux BaseOS EUS (v. 10.0)Fixed RHSA-2026:4111
Red Hat Enterprise Linux BaseOS EUS (v.9.6)Fixed RHSA-2026:2759
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:1690
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:1143
Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)Fixed RHSA-2026:4111
Red Hat Enterprise Linux Real Time (v. 10)Fixed RHSA-2026:1690
Red Hat Enterprise Linux Real Time (v. 9)Fixed RHSA-2026:1143
Red Hat Enterprise Linux Real Time EUS (v. 10.0)Fixed RHSA-2026:4111
Red Hat Enterprise Linux Real Time EUS (v.9.6)Fixed RHSA-2026:2759
Red Hat Enterprise Linux Real Time for NFV (v. 10)Fixed RHSA-2026:1690
Red Hat Enterprise Linux Real Time for NFV (v. 9)Fixed RHSA-2026:1143
Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0)Fixed RHSA-2026:4111
Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6)Fixed RHSA-2026:2759
Not affected: 3 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-38349
  2. 2026-10-03 Alias added: GHSA-c7h3-7f54-949m
  3. 2026-10-03 Fix available: Linux/Linux@263f5de8302a6f2f136d392e5d3f8b1edf922857, Linux/[email protected] · CNA
  4. 2026-10-03 1 new reference · CNA

References

Patch 5

Other 2

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

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