{"schema":"threatline.record/2","record":{"id":"CVE-2026-98061","aliases":[],"summary":"bpf: Reject tail calls directly from callback frames","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reject tail calls directly from callback frames\n\nA tail call from a non-zero frame is modeled as a return from that frame.\nThe verifier makes R0 unknown and calls prepare_func_exit() for the taken\nbranch.\n\nWhen the current frame is a synchronous callback, prepare_func_exit()\nenforces the callback return-value contract and marks R0 precise. Since the\ntail-call path synthesized R0 rather than deriving it from an instruction,\nprecision backtracking reaches the callback-calling instruction with R0\nstill requested and triggers the \"callback unexpected regs\" verifier bug.\nA CAP_BPF task can therefore cause a WARN and an -EFAULT BPF_PROG_LOAD.\n\nTail calls reachable from callbacks are already rejected later by\ncheck_max_stack_depth(). Reject a tail call made directly by a callback\nbefore constructing the inconsistent return state, using the existing\ndiagnostic. Tail calls from ordinary subprograms keep their current\nbehavior.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","source_modified_at":"2026-10-19T09:13:09.930Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"a6c22c91b6284e4713c0cf5b20ab3c9c71b77ae8","lessThan":"617c8266e49f45747f71e74177646a63f72b7025","status":"affected","versionType":"git"},{"version":"e3245f8990431950d20631c72236d4e8cb2dcde8","lessThan":"96d31b28263c429a56e4de85bcf744a5c320b3a3","status":"affected","versionType":"git"},{"version":"e3245f8990431950d20631c72236d4e8cb2dcde8","lessThan":"266aa4ad0b2e82397cd9045752c9bff03d98eddd","status":"affected","versionType":"git"},{"version":"6.18.2","lessThan":"6.18.53","status":"affected","versionType":"semver"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","source_modified_at":"2026-10-19T09:13:09.930Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"6.19","status":"affected"},{"version":"0","lessThan":"6.19","status":"unaffected","versionType":"semver"},{"version":"6.18.53","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.7","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","source_modified_at":"2026-10-19T09:13:09.930Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"617c8266e49f45747f71e74177646a63f72b7025","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","source_modified_at":"2026-10-19T09:13:09.930Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"96d31b28263c429a56e4de85bcf744a5c320b3a3","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","source_modified_at":"2026-10-19T09:13:09.930Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"266aa4ad0b2e82397cd9045752c9bff03d98eddd","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","source_modified_at":"2026-10-19T09:13:09.930Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"6.18.53","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00166,"percentile":0.05528,"score_date":"2026-10-23"},"published_at":"2026-09-25T10:24:06.001Z","modified_at":"2026-10-19T09:13:09.930Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98061","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:13:09.930Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98061","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/617c8266e49f45747f71e74177646a63f72b7025"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/96d31b28263c429a56e4de85bcf744a5c320b3a3"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/266aa4ad0b2e82397cd9045752c9bff03d98eddd"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-19T09:13:09.930Z","content_hash":"058d273145eb0099488b82178bd0f2ec3db167e467268061598c9f2a302c5dc1"}}