PT-2026-61242 · Linux · Linux

CVE-2026-63925 · Published 2026-07-19 · Updated 2026-07-19

Mitre

CVSS v3.1

8.1

High

Base vector

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

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).

Fix

Related Identifiers

CVE-2026-63925

Affected Products

Linux

References · 9

• https://nvd.nist.gov/vuln/detail/CVE-2026-63925 · Security Note
• https://git.kernel.org/stable/c/d55acbe577db892b60547b6ef1c020b359331a6d · Note
• https://git.kernel.org/stable/c/6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652 · Note
• https://git.kernel.org/stable/c/d15130461df388136b62a7b0ce9f66e7e2fa9ff1 · Note
• https://git.kernel.org/stable/c/679e13a65e68a67c8b3c0467c02ee89157ec6f0f · Note
• https://git.kernel.org/stable/c/dd7306779c6ce1238f4cdc34f3c1f2246b854457 · Note
• https://git.kernel.org/stable/c/e68842b3356471ba56c882209f324613dac47f64 · Note
• https://git.kernel.org/stable/c/79495a1b0944fe31ffd54b54b00211b493590d62 · Note
• https://git.kernel.org/stable/c/23c0e230eab397d7f68be2538790ac41d3bb91fd · Note