{"id":"CVE-2026-98084","revision":"5caf7311f24e473b897ce3a7d9a2acd9","records":[{"revision":"5caf7311f24e473b897ce3a7d9a2acd9","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-98084","aliases":[],"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":0,"publishedAt":"2026-09-25T10:24:19.881+00:00","modifiedAt":"2026-10-21T12:54:25.939+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"kernel/bpf/backtrack.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"b43550d7d58e7ae6618aaab18c1e912fa4d6e3dd\",\n                            \"lessThan\": \"1ac58dab0a83d2c64e3b807a3a0b399f17a74110\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ab5cfac139ab8576fb54630d4cca23c3e690ee90\",\n                            \"lessThan\": \"cdc93c6370f792d0649df2a145ac0cdcd430e411\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ab5cfac139ab8576fb54630d4cca23c3e690ee90\",\n                            \"lessThan\": \"3a39bc9707fbd1bef4df7318a9d02222741dda5b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ab5cfac139ab8576fb54630d4cca23c3e690ee90\",\n                            \"lessThan\": \"f83890dfed9efc5e19df1dbc1ad707a142936923\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"ab5cfac139ab8576fb54630d4cca23c3e690ee90\",\n                            \"lessThan\": \"e3e4f66cc4b72333d0886ae2673c360248987889\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"6.6.15\",\n                            \"lessThan\": \"6.6.160\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"kernel/bpf/backtrack.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.7\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.7\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.160\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.114\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.57\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.7\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/1ac58dab0a83d2c64e3b807a3a0b399f17a74110","https://git.kernel.org/stable/c/cdc93c6370f792d0649df2a145ac0cdcd430e411","https://git.kernel.org/stable/c/3a39bc9707fbd1bef4df7318a9d02222741dda5b","https://git.kernel.org/stable/c/f83890dfed9efc5e19df1dbc1ad707a142936923","https://git.kernel.org/stable/c/e3e4f66cc4b72333d0886ae2673c360248987889"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98084","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98084","identifiers":["CVE-2026-98084"]},"retained":false,"historicalAffected":[]}],"coverage":[]}