{"schema":"threatline.record/2","record":{"id":"CVE-2026-98852","aliases":[],"summary":"net: extend IPv6 exthdr detection of tunneled packets","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: extend IPv6 exthdr detection of tunneled packets\n\nCommit c4336a07eb6b (\"net: correctly handle tunneled traffic on IPV6_CSUM\nGSO fallback\") split skb_gso_has_extension_hdr() into mutually exclusive\nbranches on skb->encapsulation. This did not yet address all paths:\n\n1. With skb->encapsulation set, the outer header is not checked. IPv6\n   tunnels such as ip6_gre and ip6_tunnel add an outer Destination\n   Options header by default (encap_limit). Their GSO packets skip\n   software GSO, then skb_csum_hwoffload_help() sees the outer extension\n   header and calls skb_checksum_help() on the GSO skb, which warns and\n   drops it.\n\n2. Tunnels over IPv6 without an outer transport header, such as\n   ip6_tunnel, leave skb->transport_header at the inner transport\n   header. skb_network_header_len() then spans the outer IPv6, tunnel\n   and inner IP headers, a false positive.\n\n3. UDP tunnels without an inner network header, such as SCTP-in-UDP or\n   PSP, have no inner IPv6 header to check. Decide on the outer header\n   alone.\n\n4. Directly dereferencing inner_ip_hdr(skb)->version without\n   skb_header_pointer() is unsafe.\n\nInstead, check ipv6_ext_hdr(nexthdr) on the outer IPv6 header and, if\nset, on the inner IPv6 header. Read the headers with skb_header_pointer().\nKeep the skb_network_header_len() check when !skb->encapsulation to also\ncatch encapsulated packets without skb->encapsulation (e.g., virtio).\n\nUse the same helper in skb_csum_hwoffload_help(). Its open coded test\nhas the false positive of (2) and ignores the inner header.\n\nBackground: checksum offload of tunneled packets invariants:\n\nNon-GSO skb:\n- If the inner packet is CHECKSUM_PARTIAL, Local Checksum Offload computes\n  the outer checksum in software and the device offloads only the inner L4\n  checksum.\n- If the inner packet is CHECKSUM_NONE (e.g., SCTP-in-UDP, ESP-in-UDP,\n  Remote Checksum Offload), the device offloads the outer UDP or GRE\n  checksum instead.\n\nGSO skb:\n- A device with NETIF_F_GSO_UDP_TUNNEL_CSUM or NETIF_F_GSO_GRE_CSUM\n  computes both inner and outer checksums per segment.\n  The outer checksum is seeded with only the pseudo-header checksum.\n\nA NETIF_F_IPV6_CSUM device must parse through the outer headers to\nreach the inner ones.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","source_modified_at":"2026-10-21T12:57:32.027Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"ed71cf465c75f5688b07a35d373cd1d6b589c8ea","lessThan":"fdbd83c2d929ec968b37d2f75149a79440e328ff","status":"affected","versionType":"git"},{"version":"33670f780e0120c3dacda188c512bbffe0b6044c","lessThan":"44ba9dc568c878b699d05e7cf699572dc9df4b59","status":"affected","versionType":"git"},{"version":"a98b78116a27e2a57b696b569b2cb431c95cf9b6","lessThan":"aa480f05aed7a9eee87d4a6fc90647fe9679c670","status":"affected","versionType":"git"},{"version":"c4336a07eb6b2526dc2b62928b5104b41a7f81f5","lessThan":"cabacdf98e09eb74599c4d97d7bd7fd659598fb7","status":"affected","versionType":"git"},{"version":"c4336a07eb6b2526dc2b62928b5104b41a7f81f5","lessThan":"5f0764cb1c81a9712bce605d38efe6d844a70b29","status":"affected","versionType":"git"},{"version":"2094a7cf91b71367b649f991aacc7b579f793d0b","status":"affected","versionType":"git"},{"version":"732fdeb2987c94b439d51f5cb9addddc2fc48c42","status":"affected","versionType":"git"},{"version":"6.6.134","lessThan":"6.6.160","status":"affected","versionType":"semver"},{"version":"6.12.81","lessThan":"6.12.113","status":"affected","versionType":"semver"},{"version":"6.18.22","lessThan":"6.18.56","status":"affected","versionType":"semver"},{"version":"6.1.168","lessThan":"6.2","status":"affected","versionType":"semver"},{"version":"6.19.12","lessThan":"6.20","status":"affected","versionType":"semver"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","source_modified_at":"2026-10-21T12:57:32.027Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"7.0","status":"affected"},{"version":"0","lessThan":"7.0","status":"unaffected","versionType":"semver"},{"version":"6.6.160","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.113","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.56","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.10","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","source_modified_at":"2026-10-21T12:57:32.027Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"44ba9dc568c878b699d05e7cf699572dc9df4b59","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","source_modified_at":"2026-10-21T12:57:32.027Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"5f0764cb1c81a9712bce605d38efe6d844a70b29","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","source_modified_at":"2026-10-21T12:57:32.027Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"6.6.160","basis":"first unaffected version stated in the CVE record"},{"source":"CVE 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List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","source_modified_at":"2026-10-21T12:57:32.027Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"6.20","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00157,"percentile":0.04452,"score_date":"2026-10-23"},"published_at":"2026-10-18T15:50:55.946Z","modified_at":"2026-10-21T12:57:32.027Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98852","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T12:57:32.027Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98852","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/fdbd83c2d929ec968b37d2f75149a79440e328ff"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/44ba9dc568c878b699d05e7cf699572dc9df4b59"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/aa480f05aed7a9eee87d4a6fc90647fe9679c670"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/cabacdf98e09eb74599c4d97d7bd7fd659598fb7"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/5f0764cb1c81a9712bce605d38efe6d844a70b29"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-21T12:57:32.027Z","content_hash":"7f8f7db8f8782e12afd8d650724e6fc72a28f8fc621d2a964be5d28786e4fcd8"}}