{"id":"CVE-2026-98134","revision":"75dedc225abd417589a5971fc313929b","records":[{"revision":"75dedc225abd417589a5971fc313929b","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-98134","aliases":[],"title":"bpf: check_cond_jmp_op(): properly infer if register is null","description":"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.","state":0,"publishedAt":"2026-09-25T10:36:12.919+00:00","modifiedAt":"2026-10-21T12:54:40.601+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/verifier.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6\",\n                            \"lessThan\": \"d51cd486930f5bcfd4b55d55ab8e47b03f93d2ed\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6\",\n                            \"lessThan\": \"dfd8f8adda565e08c370c45cf9d6b2511ba9b5c6\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6\",\n                            \"lessThan\": \"9bf96b4347f541604b3caadeabda0773d9ceaf2a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6\",\n                            \"lessThan\": \"b55c9f019e169ed0d01394f96e172286a8b21b99\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"befae75856ab406a3f3fab2aa2118cf3b2dfe3e6\",\n                            \"lessThan\": \"d3ef6c097ba078e1f8c7239d76a0ce8b61e75095\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\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/verifier.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.2\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.2\",\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/d51cd486930f5bcfd4b55d55ab8e47b03f93d2ed","https://git.kernel.org/stable/c/dfd8f8adda565e08c370c45cf9d6b2511ba9b5c6","https://git.kernel.org/stable/c/9bf96b4347f541604b3caadeabda0773d9ceaf2a","https://git.kernel.org/stable/c/b55c9f019e169ed0d01394f96e172286a8b21b99","https://git.kernel.org/stable/c/d3ef6c097ba078e1f8c7239d76a0ce8b61e75095"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98134","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98134","identifiers":["CVE-2026-98134"]},"retained":false,"historicalAffected":[]}],"coverage":[]}