{"id":"CVE-2026-89579","title":"bpf: Harden bloom filter sizing and indexing on 32-bit kernels","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Harden bloom filter sizing and indexing on 32-bit kernels\n\nbloom_map_alloc() has two 32-bit-specific problems when the computed\nbitmap reaches the U32_MAX fallback…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-787"],"vendor":"Linux","product":"Linux","affected":["Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < a6183bc683f97f4317f7e84939ca7fff37c5688b","Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 80551bf8912c42d1e3d55eec6fa3c40f306c3de8","Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29","Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 272fcb4ba6fab678db0eb966dc81c4c804bef64a","Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < dff481e12b3f127739f6a4ea7cef2c25dc12e056","Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 11c1e836710dcba03e50454a4eedfdbaf8d3050e","Linux 5.16"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:49:12.203Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89579","references":[{"url":"https://git.kernel.org/stable/c/a6183bc683f97f4317f7e84939ca7fff37c5688b"},{"url":"https://git.kernel.org/stable/c/80551bf8912c42d1e3d55eec6fa3c40f306c3de8"},{"url":"https://git.kernel.org/stable/c/3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29"},{"url":"https://git.kernel.org/stable/c/272fcb4ba6fab678db0eb966dc81c4c804bef64a"},{"url":"https://git.kernel.org/stable/c/dff481e12b3f127739f6a4ea7cef2c25dc12e056"},{"url":"https://git.kernel.org/stable/c/11c1e836710dcba03e50454a4eedfdbaf8d3050e"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89579.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89579"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532482"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89579"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89579"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89579.mbox"}],"tags":["cve.org","csaf","vex","red-hat"],"epss":0.00167,"epssPercentile":0.05932,"scores":{"cna":7.8,"vendor":6.7},"ingestedAt":"2026-09-14T15:23:07.451Z","slug":"CVE-2026-89579","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Harden bloom filter sizing and indexing on 32-bit kernels\n\nbloom_map_alloc() has two 32-bit-specific problems when the computed\nbitmap reaches the U32_MAX fallback case.\n\nFirst, BITS_TO_BYTES(U32_MAX) is evaluated with 32-bit arithmetic. The\naddition performed by DIV_ROUND_UP wraps, so the map allocates only the\nfixed-size bloom filter object while keeping bitset_mask == U32_MAX.\nSubsequent updates can then write past the allocated object.\n\nSecond, fixing only the allocation size is not sufficient. The bloom hash\nis a u32, but set_bit() takes a signed long bit number and x86 test_bit()\neventually feeds the index to variable_test_bit(long, ...). On 32-bit\nkernels, hashes in [0x80000000, U32_MAX] therefore become negative bit\noffsets. x86 bt/bts with a memory operand interpret those offsets relative\nto the supplied base, so a map with bitset_mask == U32_MAX can read or\nwrite before bloom->bitset even after allocating the full 512 MiB bitmap.\n\nKeep the U32_MAX fallback, but split each hash into a word pointer and an\nin-word bit number before calling test_bit() or set_bit(). The bitops\nargument is then always in [0, BITS_PER_LONG - 1], while BIT_WORD(h) still\nselects the intended word in the full bitmap.\n\nCompute the bitset size from (u64)bitset_mask + 1 before passing the final\nsize to bpf_map_area_alloc(). This fixes the original under-allocation and\nkeeps the allocated storage consistent with the addressable bitset.\n\nExploitation note: local privilege escalation is possible on a 32-bit x86\nkernel using the under-allocation bug from a binary with CAP_BPF.\n\n## Affected\n\n- `Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < a6183bc683f97f4317f7e84939ca7fff37c5688b`\n- `Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 80551bf8912c42d1e3d55eec6fa3c40f306c3de8`\n- `Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29`\n- `Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 272fcb4ba6fab678db0eb966dc81c4c804bef64a`\n- `Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < dff481e12b3f127739f6a4ea7cef2c25dc12e056`\n- `Linux >= 9330986c03006ab1d33d243b7cfe598a7a3c1baa < 11c1e836710dcba03e50454a4eedfdbaf8d3050e`\n- `Linux 5.16`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-27 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89579.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":224704,"id":"CVE-2026-89579","ts":1792401480002,"field":"cvss","old":"6.7","new":"7.8"},{"seq":224703,"id":"CVE-2026-89579","ts":1792401480002,"field":"severity","old":"medium","new":"high"},{"seq":211831,"id":"CVE-2026-89579","ts":1790581656429,"field":"cvss","old":"7","new":"6.7"},{"seq":211830,"id":"CVE-2026-89579","ts":1790581656429,"field":"severity","old":"high","new":"medium"},{"seq":203863,"id":"CVE-2026-89579","ts":1789490210270,"field":"cvss","old":"7.8","new":"7"},{"seq":197908,"id":"CVE-2026-89579","ts":1789384320902,"field":"cvss","old":"6.7","new":"7.8"},{"seq":197907,"id":"CVE-2026-89579","ts":1789384320902,"field":"severity","old":"medium","new":"high"},{"seq":183457,"id":"CVE-2026-89579","ts":1789356675444,"field":"cvss","old":"7.8","new":"6.7"},{"seq":183456,"id":"CVE-2026-89579","ts":1789356675444,"field":"severity","old":"high","new":"medium"},{"seq":153392,"id":"CVE-2026-89579","ts":1789285350330,"field":"cvss","old":null,"new":"7.8"},{"seq":153391,"id":"CVE-2026-89579","ts":1789285350330,"field":"severity","old":"none","new":"high"},{"seq":147127,"id":"CVE-2026-89579","ts":1789270195540,"field":"cvss","old":null,"new":"6.7"},{"seq":147126,"id":"CVE-2026-89579","ts":1789270195540,"field":"severity","old":"none","new":"medium"},{"seq":108880,"id":"CVE-2026-89579","ts":1789183729379,"field":"cvss","old":null,"new":"6.7"},{"seq":108879,"id":"CVE-2026-89579","ts":1789183729379,"field":"severity","old":"none","new":"medium"}]}