CVE-2026-63925

HIGH

MEDIUM Priority: 0.03 BB Relevance: 61/100

Published: 2026-07-19 Modified: 2026-10-27 First seen: 2026-10-29 Status: active

Attack Surface

Adjacent Low Complexity No Auth No Interaction Integ. Impact

CVSS Vector Breakdown

AV: Adjacent

AC: Low

PR: None

UI: None

S: Unchanged

C: None

I: High

A: High

Description

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).