{"id":"CVE-2026-63925","title":"macsec: fix replay protection at XPN lower-PN wrap","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nmacsec: fix replay protection at XPN lower-PN wrap\n\nIn macsec_post_decrypt(), when pn is U32_MAX, pn + 1 overflows u32 to 0\nand the first branch never fires. If next_pn…","severity":"high","cvss":8.1,"cvssVector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < dd7306779c6ce1238f4cdc34f3c1f2246b854457","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < d15130461df388136b62a7b0ce9f66e7e2fa9ff1","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 23c0e230eab397d7f68be2538790ac41d3bb91fd","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 679e13a65e68a67c8b3c0467c02ee89157ec6f0f","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 79495a1b0944fe31ffd54b54b00211b493590d62","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < d55acbe577db892b60547b6ef1c020b359331a6d","Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < e68842b3356471ba56c882209f324613dac47f64","Linux 5.7"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-10-16T15:33:35.580266Z"},"published":"2026-07-19","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:42:12.466Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63925","references":[{"url":"https://git.kernel.org/stable/c/dd7306779c6ce1238f4cdc34f3c1f2246b854457"},{"url":"https://git.kernel.org/stable/c/d15130461df388136b62a7b0ce9f66e7e2fa9ff1"},{"url":"https://git.kernel.org/stable/c/23c0e230eab397d7f68be2538790ac41d3bb91fd"},{"url":"https://git.kernel.org/stable/c/679e13a65e68a67c8b3c0467c02ee89157ec6f0f"},{"url":"https://git.kernel.org/stable/c/79495a1b0944fe31ffd54b54b00211b493590d62"},{"url":"https://git.kernel.org/stable/c/6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652"},{"url":"https://git.kernel.org/stable/c/d55acbe577db892b60547b6ef1c020b359331a6d"},{"url":"https://git.kernel.org/stable/c/e68842b3356471ba56c882209f324613dac47f64"}],"tags":["cve.org"],"epss":0.00345,"epssPercentile":0.26504,"ingestedAt":"2026-10-16T17:24:46.777Z","slug":"CVE-2026-63925","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nmacsec: fix replay protection at XPN lower-PN wrap\n\nIn macsec_post_decrypt(), when pn is U32_MAX, pn + 1 overflows u32 to 0\nand the first branch never fires. If next_pn_halves.lower is also in the\nupper half, pn_same_half(pn, lower) is true and the XPN else-if does not\nfire either, leaving next_pn_halves unchanged. An attacker that captures\nthe legitimate frame carrying pn == 0xFFFFFFFF on an XPN association\ncan then replay it indefinitely, since lowest_pn never rises above\nthe captured pn and macsec_decrypt() reconstructs the same IV.\n\nExtend the XPN else-if to also fire when pn + 1 wraps to 0, so receipt\nof pn == U32_MAX advances next_pn_halves to (upper + 1, 0).\n\n## Affected\n\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < dd7306779c6ce1238f4cdc34f3c1f2246b854457`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < d15130461df388136b62a7b0ce9f66e7e2fa9ff1`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 23c0e230eab397d7f68be2538790ac41d3bb91fd`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 679e13a65e68a67c8b3c0467c02ee89157ec6f0f`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 79495a1b0944fe31ffd54b54b00211b493590d62`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < 6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < d55acbe577db892b60547b6ef1c020b359331a6d`\n- `Linux >= a21ecf0e033807b976967286e6c392f48ee2049f < e68842b3356471ba56c882209f324613dac47f64`\n- `Linux 5.7`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":45,"depthScoreParts":{"impact":44.6,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}