CVE-2026-89579
CVE-2026-89579 is a security vulnerability. O3 Security confirms whether CVE-2026-89579 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
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…
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.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-89579 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89579 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-89579. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-89579 in your dependencies?
O3 detects CVE-2026-89579 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.