{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72502", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.938Z", "datePublished": "2026-08-15T05:57:33.647Z", "dateUpdated": "2026-08-17T05:45:02.121Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:45:02.121Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)\n\nWhen MTU is large, ip6_default_advmss() can return IPV6_MAXPLEN (65535).\nThis is interpreted by TCP as mss_clamp, allowing the MSS to reach 65535.\n\nHowever, 0xFFFF is also used as a magic value GSO_BY_FRAGS in the kernel.\nIf a TCP packet with gso_size=0xFFFF is passed to skb_segment(), it will\nbe mistakenly treated as GSO_BY_FRAGS, leading to a NULL pointer\ndereference because local TCP packets do not use frag_list.\n\nFix this by returning min(IPV6_MAXPLEN, GSO_BY_FRAGS - 1) (65534) from\nip6_default_advmss() when MTU is large.\n\nAlso update the stale comment in ip6_default_advmss() which suggested\nthat IPV6_MAXPLEN is returned to mean \"any MSS\"." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - Reachable from the network via IPv6 TCP: a remote peer sends a crafted SYN (MSS=65535) or connects over a large-MTU IPv6 route, causing outbound TCP GSO skbs with gso_size=0xFFFF to be software-segmented in skb_segment() during normal packet transmit.\nAC:L - The attacker controls the TCP handshake MSS option and can induce >64KB outbound segments; syzbot reproduced this reliably, and software GSO paths (loopback, veth, NETIF_F_GSO_SOFTWARE) are common in cloud/container deployments where skb_segment() is invoked.\nPR:N - No privileges are required; exploitation occurs on the pre-authentication passive-open path where the kernel accepts a remote TCP SYN and MSS option before any application-level authentication.\nUI:N - No victim user interaction is needed beyond the target system normally accepting IPv6 TCP connections and transmitting response data to the attacker-controlled peer.\nS:U - The vulnerability causes a kernel crash on the attacked host itself; it does not cross a security boundary such as a VM escape, container sandbox breakout, or IOMMU/DMA isolation bypass.\nC:N - Impact is a NULL pointer dereference in skb_segment() when gso_size equals GSO_BY_FRAGS; there is no out-of-bounds read, use-after-free, or other memory disclosure primitive.\nI:N - The bug does not corrupt or modify attacker-controlled memory; it dereferences a NULL frag_list pointer during segmentation, yielding a crash rather than a write or code-execution primitive.\nA:H - The NULL pointer dereference in skb_segment() triggers a kernel oops/panic, causing complete loss of availability for the affected system when the malicious IPv6 TCP traffic path is exercised." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv6/route.c" ], "versions": [ { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "560b33b434e922ef97f9ff23aa2e909ef7aacd5c", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "21f69ac1879bb970588d5e7c12a96e6542f7c1a7", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "c0db3dc2ac323b6c4b76adede3b355a9daa6dea8", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "572fff10819dfc359298d1f774839e76a4d96f93", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "8e6214a530c03e341dc1b0a846c8f2b716b3551a", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "a210791f33345aa87187f7d7a9f3b9b7f4a28e6d", "status": "affected", "versionType": "git" }, { "version": "3953c46c3ac7eef31a9935427371c6f54a22f1ba", "lessThan": "2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22", "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/route.c" ], "versions": [ { "version": "4.8", "status": "affected" }, { "version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "4.8", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/560b33b434e922ef97f9ff23aa2e909ef7aacd5c" }, { "url": "https://git.kernel.org/stable/c/21f69ac1879bb970588d5e7c12a96e6542f7c1a7" }, { "url": "https://git.kernel.org/stable/c/c0db3dc2ac323b6c4b76adede3b355a9daa6dea8" }, { "url": "https://git.kernel.org/stable/c/572fff10819dfc359298d1f774839e76a4d96f93" }, { "url": "https://git.kernel.org/stable/c/8e6214a530c03e341dc1b0a846c8f2b716b3551a" }, { "url": "https://git.kernel.org/stable/c/d774cdbda6634a78d0f2baf201ee5a8c57f3bc0e" }, { "url": "https://git.kernel.org/stable/c/a210791f33345aa87187f7d7a9f3b9b7f4a28e6d" }, { "url": "https://git.kernel.org/stable/c/2bf43d0e2e6a27d52a7d624e2d6b9116972e8a22" } ], "title": "tcp: ipv6: clamp default adverting MSS to avoid GSO_BY_FRAGS (0xFFFF)", "x_generator": { "engine": "bippy-1.2.0" } } } }