net: ipv6: fix field-spanning memcpy warning in AH output
Key facts
- Attack vector
- —
- Privileges required
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- User interaction
- —
- Attack complexity
- —
- Impact type
- —
- Confidentiality · integrity · availability
- —
- Fix status
- Partial Red Hat: 5 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix field-spanning memcpy warning in AH output Fix field-spanning memcpy warnings in ah6_output() and ah6_output_done() where extension headers are copied to/from IPv6 address fields, triggering fortify-string warnings about writes beyond the 16-byte address fields. memcpy: detected field-spanning write (size 40) of single field "&top_iph->saddr" at net/ipv6/ah6.c:439 (size 16) WARNING: CPU: 0 PID: 8838 at net/ipv6/ah6.c:439 ah6_output+0xe7e/0x14e0 net/ipv6/ah6.c:439 The warnings are false positives as the extension headers are intentionally placed after the IPv6 header in memory. Fix by properly copying addresses and extension headers separately, and introduce helper functions to avoid code duplication.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 2.6.12 and later | 5.4.302, 5.10.247, 5.15.197, 6.1.159, 6.6.117, 6.12.58, 6.17.8, 6.18 | Patch available | CNA |
- Linux VendorLinux Affected 2.6.12 and later Fixed in 5.4.302, 5.10.247, 5.15.197, 6.1.159, 6.6.117, 6.12.58, 6.17.8, 6.18 Patch available CNA
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.4.302, 5.10.247, 5.15.197, 6.1.159, 6.6.117, 6.12.58, 6.17.8, 6.18
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2025-40363
- 2026-10-03 Alias added: GHSA-9gfg-vfjm-p94q
References
Other 8
- https://git.kernel.org/stable/c/2da805a61ef5272a2773775ce14c3650adb84248
- https://git.kernel.org/stable/c/9bf27de51bd6db5ff827780ec0eba55de230ba45
- https://git.kernel.org/stable/c/0bf756ae1e69fec5e6332c37830488315d6d771b
- https://git.kernel.org/stable/c/75b16b2755e12999ad850756ddfb88ad4bfc7186
- https://git.kernel.org/stable/c/f28dde240160f3c48a50d641d210ed6a3b9596ed
- https://git.kernel.org/stable/c/c14cf41094136691c92ef756872570645d61f4a1
- https://git.kernel.org/stable/c/b056f971bd72b373b7ae2025a8f3bd18f69653d3
- https://git.kernel.org/stable/c/2327a3d6f65ce2fe2634546dde4a25ef52296fec
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Sources
- CVE-2025-40363 · CVE Program
- CVE-2025-40363 · NVD
- FIRST EPSS
- GHSA-9gfg-vfjm-p94q · GitHub Advisory Database · CC BY 4.0
- CVE-2025-40363 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences