{"id":"CVE-2026-90248","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_api: fix teardown of an adopted proto on insert-race loss\n\nIn tc_new_tfilter() the create branch sets tp_created = 1 before calling\ntcf_chain_tp_insert_u…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_api: fix teardown of an adopted proto on insert-race loss\n\nIn tc_new_tfilter() the create branch sets tp_created = 1 before calling\ntcf_chain_tp_insert_u…","severity":"medium","vendor":"Linux","product":"Linux","affected":["Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < a68e664ddf16ecae6d769d6a2eb356f8abab75c9","Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < df02b6dc136af45e92ee4c86f4aa6c9a60790b1e","Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < bee2208276c8e0e40a249ffdcf6e5434a79a847c","Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < 219c87aeefdcc8c1caf28cc99e9b361ce7393d3a","Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < bbe2fd6d77df630356185406a97317f6aa6a92cf","Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < dc8b33b819cb02a75936940c120aa669ad89942d","Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 < d4e359b3608a0e184bbe8d61a5c3b50d0831c44a","Linux 5.1"],"published":"2026-09-17","updated":"2026-09-17","sourceUpdated":"2026-09-17T17:17:20.947","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-90248","references":[{"url":"https://git.kernel.org/stable/c/219c87aeefdcc8c1caf28cc99e9b361ce7393d3a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a68e664ddf16ecae6d769d6a2eb356f8abab75c9","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bbe2fd6d77df630356185406a97317f6aa6a92cf","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/bee2208276c8e0e40a249ffdcf6e5434a79a847c","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d4e359b3608a0e184bbe8d61a5c3b50d0831c44a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/dc8b33b819cb02a75936940c120aa669ad89942d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/df02b6dc136af45e92ee4c86f4aa6c9a60790b1e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-90248.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-90248"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2536663"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-90248"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90248"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90248.mbox"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"ingestedAt":"2026-09-17T16:21:47.845Z","epss":0.00211,"epssPercentile":0.11321,"cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":["CWE-911"],"slug":"CVE-2026-90248","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_api: fix teardown of an adopted proto on insert-race loss\n\nIn tc_new_tfilter() the create branch sets tp_created = 1 before calling\ntcf_chain_tp_insert_unique(). When the caller loses the race (another\nrequest inserted a proto at the same chain/prio first), insert_unique()\ndestroys the caller's own tp_new and returns the winner's proto with an\nextra reference. tp_created was never cleared, so the loser's errout\npath treated the winner's live proto as its own and called\ntcf_chain_tp_delete_empty() on it, silently unlinking an active\nclassifier that the winning request already advertised via\nRTM_NEWTFILTER.\n\nTrack the outcome of the insert step in a single tri-state variable so\neach errout path reacts correctly:\n\n- TP_NOT_CREATED: no proto created; pursue the old path.\n- TP_CREATED: proto inserted successfully; same code path as before.\n- TP_NOT_OWNED: New - lost the insert race; tp is another request's proto\n  (chain ref already released by tp_new's destroy)\n\nBoth errout reactions are single expressions derived from the state.\n\nThis fix is motivated by the Sashiko's automated review of Patch\n(net/sched: cls_api: Always acquire rtnl_lock when destroying locked\nclassifiers) [1][2]. The review identified the silent-unlink behaviour of\nan adopted proto's teardown when a request loses the\ntcf_chain_tp_insert_unique() race.\n\n[1] https://sashiko.dev/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com\n[2] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · updated 2026-10-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-90248.json)","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224338,"id":"CVE-2026-90248","ts":1792325092530,"field":"cvss","old":null,"new":"5.5"},{"seq":224337,"id":"CVE-2026-90248","ts":1792325092530,"field":"severity","old":"none","new":"medium"}]}