{"id":"CVE-2026-31680","summary":"net: ipv6: flowlabel: defer exclusive option free until RCU teardown","details":"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-\u003eopt-\u003eopt_nflen` when an option block\nis present.\n\nExclusive flowlabels currently free `fl-\u003eopt` as soon as `fl-\u003eusers`\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-\u003eopt` alive until `fl_free_rcu()`. That matches\nthe lifetime already required for the enclosing flowlabel while readers\ncan still reach it under RCU.","modified":"2026-04-26T04:22:21.568065Z","published":"2026-04-25T08:46:56.807Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31680.json"},"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/3c54b66c83fb8fcbde8e6a7bf90b65856e39f827"},{"type":"WEB","url":"https://git.kernel.org/stable/c/414726b69921fe6355ae453f5b35e68dd078342a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4b6798024f7b2d535f3db1002c760143cdbd1bd3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/572ce62778519a7d4d1c15f55dd2e45a474133c4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5a6b15f861b7c1304949e3350d23490a5fe429fd"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6c7fbdb8ffde6413640de7cfbd7c976c353e89f8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8027964931785cb73d520ac70a342a3dc16c249b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9ca562bb8e66978b53028fa32b1a190708e6a091"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31680.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31680"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d3aedd5ebd4b0b925b0bcda548066803e1318499"},{"fixed":"4b6798024f7b2d535f3db1002c760143cdbd1bd3"},{"fixed":"3c54b66c83fb8fcbde8e6a7bf90b65856e39f827"},{"fixed":"5a6b15f861b7c1304949e3350d23490a5fe429fd"},{"fixed":"6c7fbdb8ffde6413640de7cfbd7c976c353e89f8"},{"fixed":"8027964931785cb73d520ac70a342a3dc16c249b"},{"fixed":"414726b69921fe6355ae453f5b35e68dd078342a"},{"fixed":"572ce62778519a7d4d1c15f55dd2e45a474133c4"},{"fixed":"9ca562bb8e66978b53028fa32b1a190708e6a091"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31680.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.9.0"},{"fixed":"5.10.253"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.203"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.168"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.134"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.81"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.22"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.12"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31680.json"}}],"schema_version":"1.7.5"}