{"api_version":"1","generated_at":"2026-09-25T16:56:47+00:00","cve":"CVE-2026-98084","urls":{"html":"https://cve.report/CVE-2026-98084","api":"https://cve.report/api/cve/CVE-2026-98084.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98084","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98084"},"summary":{"title":"bpf: backtracking shouldn't clear outer frame R1-R5 for callbacks","description":"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'.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-25 11:17:37","updated_at":"2026-09-25 11:17:37"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/f83890dfed9efc5e19df1dbc1ad707a142936923","name":"https://git.kernel.org/stable/c/f83890dfed9efc5e19df1dbc1ad707a142936923","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/e3e4f66cc4b72333d0886ae2673c360248987889","name":"https://git.kernel.org/stable/c/e3e4f66cc4b72333d0886ae2673c360248987889","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98084","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98084","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ab5cfac139ab8576fb54630d4cca23c3e690ee90 f83890dfed9efc5e19df1dbc1ad707a142936923 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected ab5cfac139ab8576fb54630d4cca23c3e690ee90 e3e4f66cc4b72333d0886ae2673c360248987889 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected b43550d7d58e7ae6618aaab18c1e912fa4d6e3dd git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.6.15 6.7 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.7","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.7 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.7 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["kernel/bpf/backtrack.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"f83890dfed9efc5e19df1dbc1ad707a142936923","status":"affected","version":"ab5cfac139ab8576fb54630d4cca23c3e690ee90","versionType":"git"},{"lessThan":"e3e4f66cc4b72333d0886ae2673c360248987889","status":"affected","version":"ab5cfac139ab8576fb54630d4cca23c3e690ee90","versionType":"git"},{"status":"affected","version":"b43550d7d58e7ae6618aaab18c1e912fa4d6e3dd","versionType":"git"},{"lessThan":"6.7","status":"affected","version":"6.6.15","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["kernel/bpf/backtrack.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.7"},{"lessThan":"6.7","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.7","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.7","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc2","versionStartIncluding":"6.7","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.15","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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'."}],"providerMetadata":{"dateUpdated":"2026-09-25T10:24:19.881Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/f83890dfed9efc5e19df1dbc1ad707a142936923"},{"url":"https://git.kernel.org/stable/c/e3e4f66cc4b72333d0886ae2673c360248987889"}],"title":"bpf: backtracking shouldn't clear outer frame R1-R5 for callbacks","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98084","datePublished":"2026-09-25T10:24:19.881Z","dateReserved":"2026-09-25T10:19:56.075Z","dateUpdated":"2026-09-25T10:24:19.881Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-25 11:17:37","lastModifiedDate":"2026-09-25 11:17:37","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98084","Ordinal":"1","Title":"bpf: backtracking shouldn't clear outer frame R1-R5 for callback","CVE":"CVE-2026-98084","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98084","Ordinal":"1","NoteData":"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'.","Type":"Description","Title":"bpf: backtracking shouldn't clear outer frame R1-R5 for callback"}]}}}