{"id":"CVE-2026-63984","revision":"5c5222c4598045a1ad67f892eb1b5844","records":[{"revision":"5c5222c4598045a1ad67f892eb1b5844","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63984","aliases":[],"title":"ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()","description":"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.","state":0,"publishedAt":"2026-07-19T14:56:06.786+00:00","modifiedAt":"2026-10-19T20:18:00.765+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/ipv6/exthdrs.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"75b3680047bf09af8e7e471a7a6ddf2ce5847f56\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"fd238c51b0fa5390cceca9f1ac5a9ffda8063eed\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"3618b34942b76471d044369bfd30d58c39068bf1\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"97e06791368c01f0ad2a4b3269c2abe19485ca32\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"de02fc049352af5a9595f015511222d0a85c326b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"6fe1cb312038516cb4d9fa089d700af7059f1a64\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"c0487a9c1e116cf349e2d1f302d9019670460858\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3\",\n                            \"lessThan\": \"9d5e7a46a9f6d8f503b41bfefef70659845f1679\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/ipv6/exthdrs.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.7\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.7\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.259\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.210\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.176\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.143\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.93\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.35\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.0.12\",\n                            \"lessThanOrEqual\": \"7.0.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56","https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed","https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1","https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32","https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b","https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64","https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858","https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63984","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63984","identifiers":["CVE-2026-63984"]},"retained":false,"historicalAffected":[]}],"coverage":[]}