{"cve":"CVE-2025-21958","nvd":{"published":"2025-04-01T16:15:27.010","modified":"2026-07-30T06:21:59.313","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nRevert \"openvswitch: switch to per-action label counting in conntrack\"\n\nCurrently, ovs_ct_set_labels() is only called for confirmed conntrack\nentries (ct) within ovs_ct_commit(). However, if the conntrack entry\ndoes not have the labels_ext extension, attempting to allocate it in\novs_ct_get_conn_labels() for a confirmed entry triggers a warning in\nnf_ct_ext_add():\n\n  WARN_ON(nf_ct_is_confirmed(ct));\n\nThis happens when the conntrack entry is created externally before OVS\nincrements net->ct.labels_used. The issue has become more likely since\ncommit fcb1aa5163b1 (\"openvswitch: switch to per-action label counting\nin conntrack\"), which changed to use per-action label counting and\nincrement net->ct.labels_used when a flow with ct action is added.\n\nSince there’s no straightforward way to fully resolve this issue at the\nmoment, this reverts the commit to avoid breaking existing use cases.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","score":4.7},"cwes":["CWE-367"],"references":["https://git.kernel.org/stable/c/1063ae07383c0ddc5bcce170260c143825846b03","https://git.kernel.org/stable/c/9e79fdabd52cfce1a021640a81256878a2c516a2","https://git.kernel.org/stable/c/d91bfc64a4886102746e74d2c6f3a61e9a77fd7d"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:00:57.946988208+00:00"},"epss":{"cve":"CVE-2025-21958","score":0.00156,"percentile":0.04721,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}