CVE-2025-21864

Medium

In the Linux kernel, the following vulnerability has been resolved: tcp: drop secpath at the same time as we currently drop dst Xiumei reported hitting the WARN in xfrm6_tunnel_net_exit while running tests that boil down to: - create a pair of netns - run a basic TCP test over ipcomp6 - delete the pair of netns The xfrm_state found on spi_byaddr was not deleted at the time we delete the netns, because we still have a reference on it. This lingering reference comes from a secpath (which holds a ref on the xfrm_state), which is still attached to an skb. This skb is not leaked, it ends up on sk_receive_queue and then gets defer-free'd by skb_attempt_defer_free. The problem happens when we defer freeing an skb (push it on one CPU's defer_list), and don't flush that list before the netns is deleted. In that case, we still have a reference on the xfrm_state that we don't expect at this point. We already drop the skb's dst in the TCP receive path when it's no longer needed, so let's also drop the secpath. At this point, tcp_filter has already called into the LSM hooks that may require the secpath, so it should not be needed anymore. However, in some of those places, the MPTCP extension has just been attached to the skb, so we cannot simply drop all extensions.

Package Linux Kernel
Published 2025-03-12
Last modified 2026-05-12
CVSS version 3.1
Patch available
Yes

CVSS 3.1 score

5.5

out of 10
Medium
Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness type

CWE-476

CVE-2025-21864 is a NULL Pointer Dereference vulnerability

What is NULL Pointer Dereference?

The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. Learn more on MITRE CWE

Affected versions

Linux kernel versions 5.19 and later are affected. Fixed in 6.1.130, 6.6.80, 6.12.17, 6.13.5, 6.14 and their respective stable series.

Affected from
≥ 5.19
Fixed in
✓ 6.1.130 6.1.x ✓ 6.6.80 6.6.x ✓ 6.12.17 6.12.x ✓ 6.13.5 6.13.x ✓ 6.14

References

The following references provide additional information about CVE-2025-21864 including vendor advisories, patch commits, exploit details, and third-party analysis. Links are sourced from the NIST NVD database.

5 patch commits total View all on NVD

Frequently asked questions

  • What is CVE-2025-21864?

    CVE-2025-21864 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 , classified as a NULL Pointer Dereference flaw (CWE-476) . It affects Linux kernel versions from 5.19 onward and has been patched in 6.1.130, 6.6.80, 6.12.17 and others. CVE-2025-21864 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

  • What is the CVSS score for CVE-2025-21864?

    CVE-2025-21864 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H .

  • Is there a patch available for CVE-2025-21864?

    Yes — CVE-2025-21864 has been patched. Fixed versions include 6.1.130, 6.6.80, 6.12.17 and others. If you are running Linux kernel 5.19 or later up to the fix versions, apply the relevant patch for your kernel branch.

  • Is CVE-2025-21864 actively exploited?

    No — CVE-2025-21864 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

  • What is NULL Pointer Dereference (CWE-476)?

    The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. View CWE-476 on MITRE CWE →

Back to
All CVEs
View on
NVD / NIST