{"schema":"threatline.record/2","record":{"id":"CVE-2026-98084","aliases":[],"summary":"bpf: backtracking shouldn't clear outer frame R1-R5 for callbacks","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: backtracking shouldn't clear outer frame R1-R5 for callbacks\n\nWhen processing calls to bpf_loop() verifier marks R1 (and R4) as\nprecise. R1 tracks loop iterations number and because of the\n'callback_depth < R1' mechanics in check_helper_call() must be marked\nprecise. However, precision propagation for R1 was broken,\nwhen bpf_loop() call was verified on a second iteration.\n\nConsider the following verification trace:\n- main: bpf_loop(nr_loops, callback ...)\n- callback: BPF_EXIT\n- main: bpf_loop(nr_loops, callback ...)\n- ...\n\nWhile the first visit of the call to bpf_loop() propagated R1\nprecision as expected, the second call to mark_chain_precision() in\nthe check_helper_call() set R1, but it was immediately reset when\nbacktrack_insn() processed preceding BPF_EXIT in the loop deleted in\nthis patch.\n\nBecause of that, the second visit of the call to bpf_loop() injected\ncheckpoint with R1 not marked as precise. Which could trick the\nverifier into accepting unsafe programs. See the next patch for an\nexample of such program.\n\nCommit is structured in a way to minimize conflicts when\n'bpf' would be eventually merged with 'bpf-next'.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98084","source_modified_at":"2026-10-21T12:54:25.939Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"b43550d7d58e7ae6618aaab18c1e912fa4d6e3dd","lessThan":"1ac58dab0a83d2c64e3b807a3a0b399f17a74110","status":"affected","versionType":"git"},{"version":"ab5cfac139ab8576fb54630d4cca23c3e690ee90","lessThan":"cdc93c6370f792d0649df2a145ac0cdcd430e411","status":"affected","versionType":"git"},{"version":"ab5cfac139ab8576fb54630d4cca23c3e690ee90","lessThan":"3a39bc9707fbd1bef4df7318a9d02222741dda5b","status":"affected","versionType":"git"},{"version":"ab5cfac139ab8576fb54630d4cca23c3e690ee90","lessThan":"f83890dfed9efc5e19df1dbc1ad707a142936923","status":"affected","versionType":"git"},{"version":"ab5cfac139ab8576fb54630d4cca23c3e690ee90","lessThan":"e3e4f66cc4b72333d0886ae2673c360248987889","status":"affected","versionType":"git"},{"version":"6.6.15","lessThan":"6.6.160","status":"affected","versionType":"semver"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98084","source_modified_at":"2026-10-21T12:54:25.939Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"6.7","status":"affected"},{"version":"0","lessThan":"6.7","status":"unaffected","versionType":"semver"},{"version":"6.6.160","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.114","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.57","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-2026-98084","source_modified_at":"2026-10-21T12:54:25.939Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"1ac58dab0a83d2c64e3b807a3a0b399f17a74110","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98084","source_modified_at":"2026-10-21T12:54:25.939Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"3a39bc9707fbd1bef4df7318a9d02222741dda5b","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98084","source_modified_at":"2026-10-21T12:54:25.939Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"6.6.160","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00168,"percentile":0.05753,"score_date":"2026-10-23"},"published_at":"2026-09-25T10:24:19.881Z","modified_at":"2026-10-21T12:54:25.939Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98084","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T12:54:25.939Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98084","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/1ac58dab0a83d2c64e3b807a3a0b399f17a74110"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/cdc93c6370f792d0649df2a145ac0cdcd430e411"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/3a39bc9707fbd1bef4df7318a9d02222741dda5b"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/f83890dfed9efc5e19df1dbc1ad707a142936923"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e3e4f66cc4b72333d0886ae2673c360248987889"}],"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":"2026-10-21T12:54:25.939Z","content_hash":"19603b8c9b015a6f089aa09c7fc0a1666f643476d98e108a2d3e9b191c55f96e"}}