{"id":"CVE-2026-72111","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-72111","summary":"bpf: Reset register bounds before narrowing retval range in check_mem_access()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Reset register bounds before narrowing retval range in check_mem_access()\n\nWhen the BPF verifier processes a context load of an LSM hook return\nvalue, it calls __mark_reg_s32_range() to narrow the register to the\nhook's valid range. However, __mark_reg_s32_range() intersects the new\nrange with the register's existing bounds using max_t()/min_t() rather\nthan replacing them.\n\nIf the destination register carries stale bounds from a prior instruction\n(e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than\nreality. The verifier then believes it knows the register's exact value,\nwhile at runtime the actual hook return value is loaded, creating a\nverifier/runtime mismatch that can be used to bypass BPF memory safety\nchecks.\n\nThe else branch already calls mark_reg_unknown() to reset register state\nbefore any narrowing. Apply the same reset in the is_retval path so\nstale bounds are cleared before __mark_reg_s32_range() intersects.","published":"2026-08-15T05:52:52.538Z","modified":"2026-08-18T03:56:20.438698798Z","cvss":{"score":8.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.12.103"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0993dc5fc619c0b25ab1310cb11d65e78351c0fe"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5a55f9aecc08990940e70f0c7048a80850c5a16a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5e0b273e0a62cc04ec338c7b502797c66c2ed42a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bde92f65042ec14389782dd223f706bf6b59ce5d"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72111.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72111"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T03:56:20.438698798Z"}}