{"id":"CVE-2026-98802","state":"PUBLISHED","title":"seg6: ensure packet data is writable before modifying SRH and IPv6 DA","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: ensure packet data is writable before modifying SRH and IPv6 DA\n\nadvance_nextseg() modifies the SRH Segments Left field and the IPv6\ndestination address without ensuring the packet data is writable.\nseg6_next_csid_advance_arg() has the same problem when it advances the\nNEXT-C-SID argument in the destination address.\n\nThe skb may be cloned, for example by an AF_PACKET socket receiving on\nthe ingress device. advance_nextseg() and seg6_next_csid_advance_arg()\nthen write into the packet data shared with the clone. A read from that\nsocket can return the modified packet instead of the received one. The\nsimplified path below shows this for advance_nextseg():\n\n__netif_receive_skb_one_core\n  __netif_receive_skb_core\n    deliver_skb               [orig: users=2, cloned=0]\n      packet_rcv\n        skb_clone             clone queued to the AF_PACKET socket\n        consume_skb(orig)     [orig: users=1, cloned=1]\n  ipv6_rcv\n    ip6_rcv_core              skb_share_check: no-op [orig: users=1]\n    [...]\n      input_action_end_core\n        advance_nextseg       writes into the data shared with the clone\n\nCall skb_ensure_writable() in advance_nextseg() and in\nseg6_next_csid_advance_arg() before they modify the packet data.\nskb_ensure_writable() may reallocate skb->head, which invalidates the\npointers into the packet data taken before the call.\nadvance_nextseg() now returns a valid SRH pointer, or NULL if\nskb_ensure_writable() fails.\nseg6_next_csid_advance_arg() takes the pointer to the destination\naddress from the skb after skb_ensure_writable().\nOn failure, the callers drop the packet with SKB_DROP_REASON_NOMEM.","publishedAt":"2026-10-18T15:48:49.192Z","updatedAt":"2026-10-19T09:25:55.677Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"140f04c33bbcf89440dcaf8bef04918abff5a52d","status":"affected","lessThan":"e9141fdb7a2ead48cfcd60c681aba91d3014255b","versionType":"git"},{"version":"140f04c33bbcf89440dcaf8bef04918abff5a52d","status":"affected","lessThan":"8ae3f4067ba4ae3a15581392f6dac422e3d3def0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/seg6_local.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.14","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/seg6_local.c"]}],"references":["https://git.kernel.org/stable/c/e9141fdb7a2ead48cfcd60c681aba91d3014255b","https://git.kernel.org/stable/c/8ae3f4067ba4ae3a15581392f6dac422e3d3def0"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98802.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98802","state":"PUBLISHED","datePublished":"2026-10-18T15:48:49.192Z","dateUpdated":"2026-10-19T09:25:55.677Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.371Z"},"containers":{"cna":{"title":"seg6: ensure packet data is writable before modifying SRH and IPv6 DA","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: ensure packet data is writable before modifying SRH and IPv6 DA\n\nadvance_nextseg() modifies the SRH Segments Left field and the IPv6\ndestination address without ensuring the packet data is writable.\nseg6_next_csid_advance_arg() has the same problem when it advances the\nNEXT-C-SID argument in the destination address.\n\nThe skb may be cloned, for example by an AF_PACKET socket receiving on\nthe ingress device. advance_nextseg() and seg6_next_csid_advance_arg()\nthen write into the packet data shared with the clone. A read from that\nsocket can return the modified packet instead of the received one. The\nsimplified path below shows this for advance_nextseg():\n\n__netif_receive_skb_one_core\n  __netif_receive_skb_core\n    deliver_skb               [orig: users=2, cloned=0]\n      packet_rcv\n        skb_clone             clone queued to the AF_PACKET socket\n        consume_skb(orig)     [orig: users=1, cloned=1]\n  ipv6_rcv\n    ip6_rcv_core              skb_share_check: no-op [orig: users=1]\n    [...]\n      input_action_end_core\n        advance_nextseg       writes into the data shared with the clone\n\nCall skb_ensure_writable() in advance_nextseg() and in\nseg6_next_csid_advance_arg() before they modify the packet data.\nskb_ensure_writable() may reallocate skb->head, which invalidates the\npointers into the packet data taken before the call.\nadvance_nextseg() now returns a valid SRH pointer, or NULL if\nskb_ensure_writable() fails.\nseg6_next_csid_advance_arg() takes the pointer to the destination\naddress from the skb after skb_ensure_writable().\nOn failure, the callers drop the packet with SKB_DROP_REASON_NOMEM."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"140f04c33bbcf89440dcaf8bef04918abff5a52d","status":"affected","lessThan":"e9141fdb7a2ead48cfcd60c681aba91d3014255b","versionType":"git"},{"version":"140f04c33bbcf89440dcaf8bef04918abff5a52d","status":"affected","lessThan":"8ae3f4067ba4ae3a15581392f6dac422e3d3def0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/seg6_local.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.14","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/seg6_local.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e9141fdb7a2ead48cfcd60c681aba91d3014255b"},{"url":"https://git.kernel.org/stable/c/8ae3f4067ba4ae3a15581392f6dac422e3d3def0"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:25:55.677Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}