{"id":"CVE-2026-98132","summary":"bpf: don't downgrade half-dead scalar zero spills to STACK_ZERO","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: don't downgrade half-dead scalar zero spills to STACK_ZERO\n\nstates.c:__clean_func_state() can downgrade scalar zero spill to\nSTACK_ZERO in the following case:\n\n  *(u64 *)(r10 - 8) = 0;\n  ... checkpoint ...\n  r1 = *(u32 *)(r10 - 4);\n  ... no reads from r10-8 ...\n\nHere 4 bytes at r10-8 are dead and verifier changes scalar spill to a\ncombination: 0000pppp (p stands for poison). Such a change breaks\nprecision propagation chains. All places that produce STACK_ZERO\nshould call bpf_mark_chain_precision() for the zero source.\n\nThis patch fixes the bug in a simplest way possible:\navoids converting stack spills of zero to STACK_ZERO.\nTwo smarter approaches are possible:\n- do bpf_mark_chain_precision() from __clean_func_state()\n- check slot liveness information in check_stack_write_fixed_off()\n\nI investigated both and the changes required are a bit tricky,\nhence go with a simple fix for the time being.","modified":"2026-09-26T03:48:32.767093085Z","published":"2026-09-25T10:36:11.662Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98132.json","cna_assigner":"Linux"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/436fa689630b741a77ef8c4a6f426479affd5bac"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98132.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98132"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"be23266b4a08540aa43d8503a2ea10247c8daebe"},{"fixed":"436fa689630b741a77ef8c4a6f426479affd5bac"},{"fixed":"2f3536bff8823d3c5fdbbe15e17bfca696cc2b2e"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98132.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.1.0"},{"fixed":"7.2.7"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98132.json"}}],"schema_version":"1.9.0"}