{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-31680", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.130Z", "datePublished": "2026-04-25T08:46:56.807Z", "dateUpdated": "2026-08-05T12:24:26.787Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:26.787Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: flowlabel: defer exclusive option free until RCU teardown\n\n`ip6fl_seq_show()` walks the global flowlabel hash under the seq-file\nRCU read-side lock and prints `fl->opt->opt_nflen` when an option block\nis present.\n\nExclusive flowlabels currently free `fl->opt` as soon as `fl->users`\ndrops to zero in `fl_release()`. However, the surrounding\n`struct ip6_flowlabel` remains visible in the global hash table until\nlater garbage collection removes it and `fl_free_rcu()` finally tears it\ndown.\n\nA concurrent `/proc/net/ip6_flowlabel` reader can therefore race that\nearly `kfree()` and dereference freed option state, triggering a crash\nin `ip6fl_seq_show()`.\n\nFix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches\nthe lifetime already required for the enclosing flowlabel while readers\ncan still reach it under RCU." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable path is local: an attacker creates/releases IPv6 flowlabels through setsockopt(IPV6_FLOWLABEL_MGR) while reading /proc/net/ip6_flowlabel. Remote IPv6 packets do not reach this flowlabel option lifetime bug.\nAC:L - The race is between two attacker-controlled operations: flowlabel release and procfs seq-file reading. The attacker can run both sides concurrently and repeat the race without relying on external conditions.\nPR:L - Supplying the needed IPv6 option state commonly requires CAP_NET_RAW, but the check is against the socket network namespace user_ns and is reachable with low privileges via user namespaces. No real init-namespace root/admin privilege is required in the highest reasonable deployment scenario.\nUI:N - The attacker can create the socket state, release it, and read /proc/net/ip6_flowlabel directly. No victim action is required.\nS:U - This is a kernel memory lifetime bug within the same host kernel security authority. It does not cross a VM, IOMMU, or separate authorization boundary.\nC:H - The bug is a use-after-free of struct ipv6_txoptions reachable from procfs output, and freed kernel heap contents can be exposed or attacker-shaped. Per the required conservative guidance, kernel UAFs are scored High for confidentiality.\nI:H - Although the observed dereference is a stale read, this is a kernel heap use-after-free in attacker-reclaimable memory. Per the required conservative guidance and upward scoring on uncertainty, UAFs are scored High for integrity.\nA:H - A concurrent /proc/net/ip6_flowlabel reader can dereference freed option state in ip6fl_seq_show(), causing an oops or kernel crash. Kernel crashes are High availability impact." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv6/ip6_flowlabel.c" ], "versions": [ { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "4b6798024f7b2d535f3db1002c760143cdbd1bd3", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "3c54b66c83fb8fcbde8e6a7bf90b65856e39f827", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "5a6b15f861b7c1304949e3350d23490a5fe429fd", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "6c7fbdb8ffde6413640de7cfbd7c976c353e89f8", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "8027964931785cb73d520ac70a342a3dc16c249b", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "414726b69921fe6355ae453f5b35e68dd078342a", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "572ce62778519a7d4d1c15f55dd2e45a474133c4", "status": "affected", "versionType": "git" }, { "version": "d3aedd5ebd4b0b925b0bcda548066803e1318499", "lessThan": "9ca562bb8e66978b53028fa32b1a190708e6a091", "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/ip6_flowlabel.c" ], "versions": [ { "version": "3.9", "status": "affected" }, { "version": "0", "lessThan": "3.9", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.253", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.203", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.168", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.134", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.81", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.22", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.12", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0", "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": "3.9", "versionEndExcluding": "5.10.253" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "5.15.203" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "6.1.168" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "6.6.134" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "6.12.81" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "6.18.22" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "6.19.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.9", "versionEndExcluding": "7.0" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3" }, { "url": "https://git.kernel.org/stable/c/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827" }, { "url": "https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd" }, { "url": "https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8" }, { "url": "https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b" }, { "url": "https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a" }, { "url": "https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4" }, { "url": "https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091" } ], "title": "net: ipv6: flowlabel: defer exclusive option free until RCU teardown", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "x_adpType": "supplier", "providerMetadata": { "orgId": 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