{"api_version":"1","generated_at":"2026-07-23T21:48:03+00:00","cve":"CVE-2026-63984","urls":{"html":"https://cve.report/CVE-2026-63984","api":"https://cve.report/api/cve/CVE-2026-63984.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63984","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63984"},"summary":{"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":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:17","updated_at":"2026-07-20 15:17:00"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64","name":"https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1","name":"https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858","name":"https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed","name":"https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32","name":"https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b","name":"https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679","name":"https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56","name":"https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63984","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63984","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 75b3680047bf09af8e7e471a7a6ddf2ce5847f56 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 fd238c51b0fa5390cceca9f1ac5a9ffda8063eed git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 3618b34942b76471d044369bfd30d58c39068bf1 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 97e06791368c01f0ad2a4b3269c2abe19485ca32 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"63984","cve":"CVE-2026-63984","epss":"0.001760000","percentile":"0.073880000","score_date":"2026-07-20","updated_at":"2026-07-21 00:13:13"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/ipv6/exthdrs.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"75b3680047bf09af8e7e471a7a6ddf2ce5847f56","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"fd238c51b0fa5390cceca9f1ac5a9ffda8063eed","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"3618b34942b76471d044369bfd30d58c39068bf1","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"97e06791368c01f0ad2a4b3269c2abe19485ca32","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"de02fc049352af5a9595f015511222d0a85c326b","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"6fe1cb312038516cb4d9fa089d700af7059f1a64","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"c0487a9c1e116cf349e2d1f302d9019670460858","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"},{"lessThan":"9d5e7a46a9f6d8f503b41bfefef70659845f1679","status":"affected","version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/ipv6/exthdrs.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.7"},{"lessThan":"5.7","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.259","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.210","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.176","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.143","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.93","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.35","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.12","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.259","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.210","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.176","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.143","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.93","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.35","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.12","versionStartIncluding":"5.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1","versionStartIncluding":"5.7","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-20T13:42:04.995Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56"},{"url":"https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"},{"url":"https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1"},{"url":"https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32"},{"url":"https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"},{"url":"https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64"},{"url":"https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858"},{"url":"https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"}],"title":"ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63984","datePublished":"2026-07-19T14:56:06.786Z","dateReserved":"2026-07-19T07:54:57.025Z","dateUpdated":"2026-07-20T13:42:04.995Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 16:17:17","lastModifiedDate":"2026-07-20 15:17:00","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63984","Ordinal":"1","Title":"ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()","CVE":"CVE-2026-63984","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63984","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()"}]}}}