{"id":"CVE-2026-98802","summary":"seg6: ensure packet data is writable before modifying SRH and IPv6 DA","details":"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-\u003ehead, 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.","modified":"2026-10-19T02:47:27.241694094Z","published":"2026-10-18T15:48:49.192Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98802.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8ae3f4067ba4ae3a15581392f6dac422e3d3def0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e9141fdb7a2ead48cfcd60c681aba91d3014255b"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98802.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98802"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"140f04c33bbcf89440dcaf8bef04918abff5a52d"},{"fixed":"e9141fdb7a2ead48cfcd60c681aba91d3014255b"},{"fixed":"8ae3f4067ba4ae3a15581392f6dac422e3d3def0"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98802.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.14.0"},{"fixed":"7.2.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98802.json"}}],"schema_version":"1.9.0"}