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VulnerabilityPublished Updated

CVE-2025-21867: Linux kernel · bpf, test_run: Fix use-after-free issue in eth_skb_pkt_type()

Affects Linux kernelSource GCVE Database

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Not known to be exploited · CVSS 7.8 High.

Data as of 10 Nov 2026, 13:49 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.

Sources agree

CVSS scores by source
CNA (Linux)CVSS 3.17.8
CISA-ADPCVSS 3.17.8
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Mar 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel by adding proper validation of the user_data parameter in bpf_test_init(). Users and administrators should apply the official Linux kernel updates that include this patch to remediate the issue. Since this is not a cloud service, manual patching is required. Patch status is confirmed by the vendor advisory describing the fix. No additional mitigations are indicated.

Description

CVE-2025-21867 is a use-after-free vulnerability in the Linux kernel's eth_skb_pkt_type() function. The flaw occurs when eth_skb_pkt_type() accesses skb data that does not contain an Ethernet header, triggered by invalid user_data passed to bpf_test_init() via bpf_prog_test_run_xdp(). This issue was detected by KMSAN and fixed by adding a check to return an error if user_data is less than the Ethernet header length (ETH_HLEN).

References

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