{"id":"CVE-2026-98049","state":"PUBLISHED","title":"bpf: zero extend the result of an arena 32-bit cmpxchg","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: zero extend the result of an arena 32-bit cmpxchg\n\nbpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from\nBPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before\nbpf_opt_subreg_zext_lo32_rnd_hi32().\n\nThat pass emits an explicit zero extension for a 32-bit cmpxchg even\nwhen bpf_jit_needs_zext() is false. This is done because on some\narchitectures 32-bit cmpxchg requires explicit zero extension for the\ndst register. E.g. on x86-64 'lock cmpxchg' does not change the %eax\nif comparison is successful, while BPF semantics declare that each\noperation on a 32-bit register zero extends it's upper half.\n\nis_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena\ncmpxchg misses said zero extension adjustment. This patch adjusts\nis_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC.","publishedAt":"2026-09-25T10:23:58.561Z","updatedAt":"2026-10-21T12:54:16.141Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"1bb1be18263995b159cf5afad3a05500ba6d2a7b","versionType":"git"},{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"6bb6ae5ab1beffda51dabf41612f501d07f10fc6","versionType":"git"},{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"1c1b476d43a8b6c9bc04600369dd8cc39950d98e","versionType":"git"},{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"4814ed6406f3493bd554ad046da5f7fc04833571","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/fixups.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/fixups.c"]}],"references":["https://git.kernel.org/stable/c/1bb1be18263995b159cf5afad3a05500ba6d2a7b","https://git.kernel.org/stable/c/6bb6ae5ab1beffda51dabf41612f501d07f10fc6","https://git.kernel.org/stable/c/1c1b476d43a8b6c9bc04600369dd8cc39950d98e","https://git.kernel.org/stable/c/4814ed6406f3493bd554ad046da5f7fc04833571"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98049.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98049","state":"PUBLISHED","datePublished":"2026-09-25T10:23:58.561Z","dateUpdated":"2026-10-21T12:54:16.141Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:19:56.072Z"},"containers":{"cna":{"title":"bpf: zero extend the result of an arena 32-bit cmpxchg","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: zero extend the result of an arena 32-bit cmpxchg\n\nbpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from\nBPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before\nbpf_opt_subreg_zext_lo32_rnd_hi32().\n\nThat pass emits an explicit zero extension for a 32-bit cmpxchg even\nwhen bpf_jit_needs_zext() is false. This is done because on some\narchitectures 32-bit cmpxchg requires explicit zero extension for the\ndst register. E.g. on x86-64 'lock cmpxchg' does not change the %eax\nif comparison is successful, while BPF semantics declare that each\noperation on a 32-bit register zero extends it's upper half.\n\nis_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena\ncmpxchg misses said zero extension adjustment. This patch adjusts\nis_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"1bb1be18263995b159cf5afad3a05500ba6d2a7b","versionType":"git"},{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"6bb6ae5ab1beffda51dabf41612f501d07f10fc6","versionType":"git"},{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"1c1b476d43a8b6c9bc04600369dd8cc39950d98e","versionType":"git"},{"version":"d503a04f8bc0c75dc9db9452d8cc79d748afb752","status":"affected","lessThan":"4814ed6406f3493bd554ad046da5f7fc04833571","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/fixups.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.10","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.10","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/bpf/fixups.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1bb1be18263995b159cf5afad3a05500ba6d2a7b"},{"url":"https://git.kernel.org/stable/c/6bb6ae5ab1beffda51dabf41612f501d07f10fc6"},{"url":"https://git.kernel.org/stable/c/1c1b476d43a8b6c9bc04600369dd8cc39950d98e"},{"url":"https://git.kernel.org/stable/c/4814ed6406f3493bd554ad046da5f7fc04833571"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-21T12:54:16.141Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.10","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}