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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-89579
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:19:42 UTC
Updated2026-09-14 13:19:12 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001660000 probability, percentile 0.062220000 (date 2026-09-14)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa a6183bc683f97f4317f7e84939ca7fff37c5688b git Not specified
CNA Linux Linux affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa 80551bf8912c42d1e3d55eec6fa3c40f306c3de8 git Not specified
CNA Linux Linux affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa 3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29 git Not specified
CNA Linux Linux affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa 272fcb4ba6fab678db0eb966dc81c4c804bef64a git Not specified
CNA Linux Linux affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa dff481e12b3f127739f6a4ea7cef2c25dc12e056 git Not specified
CNA Linux Linux affected 9330986c03006ab1d33d243b7cfe598a7a3c1baa 11c1e836710dcba03e50454a4eedfdbaf8d3050e git Not specified
CNA Linux Linux affected 5.16 Not specified
CNA Linux Linux unaffected 5.16 semver Not specified
CNA Linux Linux unaffected 6.1.188 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a6183bc683f97f4317f7e84939ca7fff37c5688b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dff481e12b3f127739f6a4ea7cef2c25dc12e056 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/272fcb4ba6fab678db0eb966dc81c4c804bef64a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/80551bf8912c42d1e3d55eec6fa3c40f306c3de8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/11c1e836710dcba03e50454a4eedfdbaf8d3050e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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