CVE-2025-40363

Fortify warning via field-spanning AH copy

Published Dec 16, 2025 · Updated Dec 16, 2025

Fortify-string diagnostics in the Linux IPv6 AH output path trigger a kernel warning when extension headers are copied. In ah6_output() and ah6_output_done(), memcpy spans 16-byte IPv6 address fields into adjacent extension-header storage, so fortify-string treats intentional contiguous layout as an overrun. The condition requires IPv6 Authentication Header output with extension headers, and the Linux CNA identifies it as a false positive with no reported memory corruption or attacker-controlled consequence.

CVSS severityUnavailable
Unscored
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Fortify-string diagnostics in the Linux IPv6 AH output path trigger a kernel warning when extension headers are copied. In ah6_output() and ah6_output_done(), memcpy spans 16-byte IPv6 address fields into adjacent extension-header storage, so fortify-string treats intentional contiguous layout as an overrun. The condition requires IPv6 Authentication Header output with extension headers, and the Linux CNA identifies it as a false positive with no reported memory corruption or attacker-controlled consequence.

The record

CVE
CVE-2025-40363
Published
Dec 16, 2025
Updated
Dec 16, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 16, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0bf756ae1e69fec5e6332c37830488315d6d771b
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2327a3d6f65ce2fe2634546dde4a25ef52296fec
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2da805a61ef5272a2773775ce14c3650adb84248
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <75b16b2755e12999ad850756ddfb88ad4bfc7186
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9bf27de51bd6db5ff827780ec0eba55de230ba45
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b056f971bd72b373b7ae2025a8f3bd18f69653d3
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c14cf41094136691c92ef756872570645d61f4a1
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f28dde240160f3c48a50d641d210ed6a3b9596ed

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <0bf756ae1e69fec5e6332c37830488315d6d771b; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2327a3d6f65ce2fe2634546dde4a25ef52296fec; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2da805a61ef5272a2773775ce14c3650adb84248; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <75b16b2755e12999ad850756ddfb88ad4bfc7186; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9bf27de51bd6db5ff827780ec0eba55de230ba45; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b056f971bd72b373b7ae2025a8f3bd18f69653d3; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c14cf41094136691c92ef756872570645d61f4a1; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f28dde240160f3c48a50d641d210ed6a3b9596ed

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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