{"schema_version":"1.9.0","id":"CVE-2026-63984","published":"2026-07-19T14:56:06.786Z","modified":"2026-08-31T18:26:09.268253360Z","related":["SUSE-SU-2026:23193-1","SUSE-SU-2026:23194-1","SUSE-SU-2026:23241-1","SUSE-SU-2026:23244-1","SUSE-SU-2026:3593-1","SUSE-SU-2026:3595-1","SUSE-SU-2026:3602-1","SUSE-SU-2026:3616-1","SUSE-SU-2026:3617-1","SUSE-SU-2026:3790-1","SUSE-SU-2026:3810-1"],"summary":"ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()\n\nipv6_rpl_srh_decompress() computes:\n\n    outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);\n\nhdrlen is __u8. For n >= 127 the result exceeds 255 and silently\ntruncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n\n    (128 * 16) >> 3 = 256, truncated to 0 as __u8\n\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\n\nThe existing guard at exthdrs.c:546 checks (n + 1) > 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not\nfit.\n\nTighten the bound to (n + 1) > 127. This caps n at 126, giving\nhdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment.","affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3"},{"fixed":"75b3680047bf09af8e7e471a7a6ddf2ce5847f56"},{"fixed":"fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"},{"fixed":"3618b34942b76471d044369bfd30d58c39068bf1"},{"fixed":"97e06791368c01f0ad2a4b3269c2abe19485ca32"},{"fixed":"de02fc049352af5a9595f015511222d0a85c326b"},{"fixed":"6fe1cb312038516cb4d9fa089d700af7059f1a64"},{"fixed":"c0487a9c1e116cf349e2d1f302d9019670460858"},{"fixed":"9d5e7a46a9f6d8f503b41bfefef70659845f1679"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63984.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.7.0"},{"fixed":"5.10.259"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.210"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.176"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.143"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.93"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.35"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63984.json"}}],"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64"},{"type":"WEB","url":"https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56"},{"type":"WEB","url":"https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858"},{"type":"WEB","url":"https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63984.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63984"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63984.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}