CVE-2026-63925

Summary

In the Linux kernel, the following vulnerability has been resolved: macsec: fix replay protection at XPN lower-PN wrap In macsec_post_decrypt(), when pn is U32_MAX, pn + 1 overflows u32 to 0 and the first branch never fires. If next_pn_halves.lower is also in the upper half, pn_same_half(pn, lower) is true and the XPN else-if does not fire either, leaving next_pn_halves unchanged. An attacker that captures the legitimate frame carrying pn == 0xFFFFFFFF on an XPN association can then replay it indefinitely, since lowest_pn never rises above the captured pn and macsec_decrypt() reconstructs the same IV. Extend the XPN else-if to also fire when pn + 1 wraps to 0, so receipt of pn == U32_MAX advances next_pn_halves to (upper + 1, 0).

Impact & exploitability

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Affected products we track (1)

Recommendation

Apply the vendor fix promptly. Open any affected product above for its exact safe version.

Official patch: https://git.kernel.org/stable/c/23c0e230eab397d7f68be2538790ac41d3bb91fd ↗

Additional information

• NVD record
• https://git.kernel.org/stable/c/23c0e230eab397d7f68be2538790ac41d3bb91fdPatch
• https://git.kernel.org/stable/c/679e13a65e68a67c8b3c0467c02ee89157ec6f0fPatch
• https://git.kernel.org/stable/c/6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652Patch
• https://git.kernel.org/stable/c/79495a1b0944fe31ffd54b54b00211b493590d62Patch
• https://git.kernel.org/stable/c/d15130461df388136b62a7b0ce9f66e7e2fa9ff1Patch
• https://git.kernel.org/stable/c/d55acbe577db892b60547b6ef1c020b359331a6dPatch
• https://git.kernel.org/stable/c/dd7306779c6ce1238f4cdc34f3c1f2246b854457Patch
• https://git.kernel.org/stable/c/e68842b3356471ba56c882209f324613dac47f64Patch