CVE-2026-89579bpf: Harden bloom filter sizing and indexing on 32-bit kernels

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Harden bloom filter sizing and indexing on 32-bit kernels bloom_map_alloc() has two 32-bit-specific problems when the computed bitmap reaches the U32_MAX fallback case. First, BITS_TO_BYTES(U32_MAX) is evaluated with 32-bit arithmetic. The addition performed by DIV_ROUND_UP wraps, so the map allocates only the fixed-size bloom filter object while keeping bitset_mask == U32_MAX. Subsequent updates can then write past the allocated object. Second, fixing only the allocation size is not sufficient. The bloom hash is a u32, but set_bit() takes a signed long bit number and x86 test_bit() eventually feeds the index to variable_test_bit(long, ...). On 32-bit kernels, hashes in [0x80000000, U32_MAX] therefore become negative bit offsets. x86 bt/bts with a memory operand interpret those offsets relative to the supplied base, so a map with bitset_mask == U32_MAX can read or write before bloom->bitset even after allocating the full 512 MiB bitmap. Keep the U32_MAX fallback, but split each hash into a word pointer and an in-word bit number before calling test_bit() or set_bit(). The bitops argument is then always in [0, BITS_PER_LONG - 1], while BIT_WORD(h) still selects the intended word in the full bitmap. Compute the bitset size from (u64)bitset_mask + 1 before passing the final size to bpf_map_area_alloc(). This fixes the original under-allocation and keeps the allocated storage consistent with the addressable bitset. Exploitation note: local privilege escalation is possible on a 32-bit x86 kernel using the under-allocation bug from a binary with CAP_BPF.

Timeline

Scores

EPSS (exploitation in 30 days)

0.17% · top 94% of all CVEs (13 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Affected products

• Linux · Linux

  • affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa – < a6183bc683f97f4317f7e84939ca7fff37c5688b
  • affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa – < 80551bf8912c42d1e3d55eec6fa3c40f306c3de8
  • affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa – < 3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29
  • affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa – < 272fcb4ba6fab678db0eb966dc81c4c804bef64a
  • affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa – < dff481e12b3f127739f6a4ea7cef2c25dc12e056
  • affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa – < 11c1e836710dcba03e50454a4eedfdbaf8d3050e

• Linux · Linux

  • affected 5.16
  • unaffected < 5.16
  • unaffected 6.1.188 – ≤ 6.1.*
  • unaffected 6.6.157 – ≤ 6.6.*
  • unaffected 6.12.109 – ≤ 6.12.*
  • unaffected 6.18.50 – ≤ 6.18.*
  • unaffected 7.2.4 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-76491 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-89579](https://cveledger.app/badge/CVE-2026-89579.svg)](https://cveledger.app/cve/CVE-2026-89579)

Record last updated 19 Oct 2026, 08:49 UTC.