{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63984","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-07-19T07:54:57.025Z","datePublished":"2026-07-19T14:56:06.786Z","dateUpdated":"2026-08-05T12:37:52.442Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:37:52.442Z"},"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":{"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"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable code runs in the IPv6 routing-header receive handler on incoming packets; a remote attacker can deliver a crafted RFC 6554 type-3 RPL SRH to an RPL-enabled router or gateway over the network.\nAC:L - Triggering requires only a deterministically crafted SRH (e.g., n=127, CmprI=15, CmprE=15, pad=0, hdrlen=16, segments_left>0); all of these fields are fully attacker-controlled once the target has rpl_seg_enabled.\nPR:N - No authentication or local privileges are needed to send the malicious IPv6 packet; rpl_seg_enabled is a victim-side deployment setting on RPL routers/gateways (IoT/industrial mesh), not an attacker privilege requirement.\nUI:N - Exploitation is achieved solely by sending a malformed network packet and does not require any action from a victim user.\nS:U - Impact is confined to kernel memory corruption and packet forwarding within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The hdrlen truncation causes overlapping read/write of the same kmalloc buffer during decompress/recompress, constituting kernel heap memory corruption that can be leveraged for information disclosure primitives.\nI:H - ipv6_rpl_srh_compress() performs out-of-bounds writes into the overlapping decompressed region, corrupting routing-header data that is then memcpy'd into the forwarded skb, enabling memory corruption exploitable for control-flow or data modification.\nA:H - Kernel heap corruption during SRH processing can cause kernel oops, panics, or repeated crashes when processing or forwarding the corrupted packet, consistent with high availability impact for memory-corruption bugs."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/exthdrs.c"],"versions":[{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"75b3680047bf09af8e7e471a7a6ddf2ce5847f56","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"fd238c51b0fa5390cceca9f1ac5a9ffda8063eed","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"3618b34942b76471d044369bfd30d58c39068bf1","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"97e06791368c01f0ad2a4b3269c2abe19485ca32","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"de02fc049352af5a9595f015511222d0a85c326b","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"6fe1cb312038516cb4d9fa089d700af7059f1a64","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"c0487a9c1e116cf349e2d1f302d9019670460858","status":"affected","versionType":"git"},{"version":"8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3","lessThan":"9d5e7a46a9f6d8f503b41bfefef70659845f1679","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/exthdrs.c"],"versions":[{"version":"5.7","status":"affected"},{"version":"0","lessThan":"5.7","status":"unaffected","versionType":"semver"},{"version":"5.10.259","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.210","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.176","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.143","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.93","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.35","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.0.12","lessThanOrEqual":"7.0.*","status":"unaffected","versionType":"semver"},{"version":"7.1","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.10.259"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.15.210"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.1.176"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.12.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"6.18.35"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"7.0.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"7.1"}]}]}],"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"}}}}