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CVE-2026-89579

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.8 · Élevée
EPSS 0.2%
Linux•Linux•Versions : <=6.1.*, <=6.12.*, 5.16, 0, 7.2.4, 6.1.188, <a6183bc683f97f4317f7e84939ca7fff37c5688b, <=6.6.*, <dff481e12b3f127739f6a4ea7cef2c25dc12e056, 6.6.157, <80551bf8912c42d1e3d55eec6fa3c40f306c3de8, <272fcb4ba6fab678db0eb966dc81c4c804bef64a, <5.16, <=6.18.*, <=7.2.*, <=*, <3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29, <11c1e836710dcba03e50454a4eedfdbaf8d3050e, 9330986c03006ab1d33d243b7cfe598a7a3c1baa, 6.18.50, 6.12.109, 7.3

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.

Gravité et risque d'exploitation

CVE-2026-89579 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.17 %, ce qui la place devant 5.6 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 5.16, 0, 7.2.4, 6.1.188, <a6183bc683f97f4317f7e84939ca7fff37c5688b, <=6.6.*, <dff481e12b3f127739f6a4ea7cef2c25dc12e056, 6.6.157, <80551bf8912c42d1e3d55eec6fa3c40f306c3de8, <272fcb4ba6fab678db0eb966dc81c4c804bef64a, <5.16, <=6.18.*, <=7.2.*, <=*, <3b7a13eccfcf97714ffc1ca6aa663d66d4a30e29, <11c1e836710dcba03e50454a4eedfdbaf8d3050e, 9330986c03006ab1d33d243b7cfe598a7a3c1baa, 6.18.50, 6.12.109, 7.3) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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