CVE-2025-21867: Linux kernel · bpf, test_run: Fix use-after-free issue in eth_skb_pkt_type()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High.
Data as of 10 Nov 2026, 13:49 UTC
Sources agree
| CNA (Linux) | CVSS 3.1 | 7.8 |
|---|---|---|
| CISA-ADP | CVSS 3.1 | 7.8 |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Mar 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
- git.kernel.org/stable/c/f615fccfc689cb48977d275ac2e391297b52392b (opens in a new tab)
- git.kernel.org/stable/c/d56d8a23d95100b65f40438639dd82db2af81c11 (opens in a new tab)
- git.kernel.org/stable/c/972bafed67ca73ad9a56448384281eb5fd5c0ba3 (opens in a new tab)
- git.kernel.org/stable/c/1a9e1284e87d59b1303b69d1808d310821d6e5f7 (opens in a new tab)
- git.kernel.org/stable/c/6b3d638ca897e099fa99bd6d02189d3176f80a47 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2025/05/msg00045.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-019113.html (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-457936.html (opens in a new tab)