{"schema":"threatline.record/2","record":{"id":"CVE-2026-98134","aliases":[],"summary":"bpf: check_cond_jmp_op(): properly infer if register is null","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: check_cond_jmp_op(): properly infer if register is null\n\nNicholas Carlini reported a bug when verifier can incorrectly infer\nthat a pointer is non-null. The bug occurs when two pointers are\ncompared and one of them has a type w/o PTR_MAYBE_NULL flag,\nbut which allows a value to be NULL at runtime.\nHere is an example:\n\n  // `a` is PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED\n  // `a` is 0 at runtime.\n  // `b` is PTR_TO_MAP_VALUE | PTR_MAYBE_NULL\n  void *a = bpf_rdonly_cast(0, 0);\n  int  *b = bpf_map_lookup_elem(...);\n\n  if (a == b)\n    *b = 42;  // verifier does not catch null pointer dereference\n\nThis happens because of a special case in check_cond_jmp_op(),\nwhich attempts to strip PTR_MAYBE_NULL flags from pointer types,\nwhen processing comparisons like `rA == rB`, if either rA or rB can't\nbe null.\n\nThe non-null property is derived based on the absence of\nPTR_MAYBE_NULL flag on rA's or rB's type. But that is not sufficient\nfor types like PTR_TO_MEM, as in the example.\n\nThis patch replaces type_may_be_null() call with reg_not_null(),\nwhich contains an allowlist of types for which absence of\nPTR_MAYBE_NULL actually means that the value can't be NULL at runtime.\n\nAt the moment, the list in the reg_not_null() omits two types for\nwhich PTR_MAYBE_NULL is applicable: PTR_TO_XDP_SOCK and PTR_TO_BUF.\nIn order to remain backward compatible, and assuming that only\ncomparison between pointers of the same type makes sense,\nthis commit extends reg_not_null(). W/o such an extension e.g.\nverifier_jeq_infer_not_null/null_ptr_to_map_value fails.\n\nreg_not_null() can be extended further, but I deem that out of scope\nfor the fix at hand. Explicit base_type(...) != PTR_TO_BTF_ID\nchecks in the check_cond_jmp_op() can be removed with migration to\nreg_not_null(), but that is a behavioural change, as the special case\nwould start matching for PTR_TO_BTF_ID that is also is_trusted_reg().\nI omit the behavioural change from this commit.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98134","source_modified_at":"2026-10-21T12:54:40.601Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6","lessThan":"d51cd486930f5bcfd4b55d55ab8e47b03f93d2ed","status":"affected","versionType":"git"},{"version":"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6","lessThan":"dfd8f8adda565e08c370c45cf9d6b2511ba9b5c6","status":"affected","versionType":"git"},{"version":"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6","lessThan":"9bf96b4347f541604b3caadeabda0773d9ceaf2a","status":"affected","versionType":"git"},{"version":"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6","lessThan":"b55c9f019e169ed0d01394f96e172286a8b21b99","status":"affected","versionType":"git"},{"version":"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6","lessThan":"d3ef6c097ba078e1f8c7239d76a0ce8b61e75095","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98134","source_modified_at":"2026-10-21T12:54:40.601Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"6.2","status":"affected"},{"version":"0","lessThan":"6.2","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-2026-98134","source_modified_at":"2026-10-21T12:54:40.601Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"9bf96b4347f541604b3caadeabda0773d9ceaf2a","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00122,"percentile":0.01858,"score_date":"2026-10-23"},"published_at":"2026-09-25T10:36:12.919Z","modified_at":"2026-10-21T12:54:40.601Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98134","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T12:54:40.601Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98134","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/d51cd486930f5bcfd4b55d55ab8e47b03f93d2ed"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/dfd8f8adda565e08c370c45cf9d6b2511ba9b5c6"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/9bf96b4347f541604b3caadeabda0773d9ceaf2a"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/b55c9f019e169ed0d01394f96e172286a8b21b99"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/d3ef6c097ba078e1f8c7239d76a0ce8b61e75095"}],"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":"2026-10-21T12:54:40.601Z","content_hash":"bb64769c3180c908ffb293d3481c60ce89feda74a19611e5ac880ac52e822c2c"}}