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CVE-2026-74612

Vulnérabilité critique dans Linux (Linux)

CVSS 10.0 · Critique
EPSS 0.5%
Linux•Linux•Versions : <=6.1.*, <=6.12.*, 6.6.152, 5.18, <41b96667d42b74bb4b137f1bb78b611a953c5943, 0, <cb6379feaaff11c4e1e79c26c745ffa23182768a, <=7.1.*, <5.18, <=6.6.*, 7.1.9, <=6.18.*, 6.1.184, 6.12.104, <2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139, 718a18a0c8a67f97781e40bdef7cdd055c430996, 6.18.45, <=*, <3205b0652a37255dbb7ca8f3d942c8d8aa677c21, <cdf745b7a777f87f51666e5d8f4c6fc279bcf54d, <0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5, 7.2

Description

In the Linux kernel, the following vulnerability has been resolved: veth: fix skb length accounting after XDP frag adjustment veth exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, veth_xdp_rcv_skb() copies xdp_frags_size back to skb->data_len but leaves skb->len containing the old fragment contribution. After a fragment shrink, this makes skb_headlen() larger than the actual linear area. In the reproduced UDP receive path, __skb_datagram_iter() copied 1024 bytes past the actual linear tail to userspace, starting at struct skb_shared_info. The copied bytes included the affected skb's nr_frags, xdp_frags_size, and a kernel pointer from skb_shinfo(skb)->frags[0]. Real packet data was displaced by the same amount and truncated at the end. Subtract the old data_len before replacing it and add the new data_len afterwards, keeping skb->len and skb->data_len synchronized. Additionally, bpf_xdp_pull_data() can advance data_end while leaving frags present. The skb is then still non-linear, so the old __skb_put(skb, off) triggers SKB_LINEAR_ASSERT(). Use skb_set_tail_pointer() and update skb->len explicitly instead, following bpf_prog_run_generic_xdp(). Unlike __skb_put(), skb_set_tail_pointer() does not require a linear skb. A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by 1024 bytes from its fragment area. Before the fix, all 10 runs produced corrupted payloads. After the fix, all 10 runs matched the expected payload exactly. A forced-tailroom reproducer also exercises bpf_xdp_pull_data() with frags still present; the old code triggers SKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.

Gravité et risque d'exploitation

CVE-2026-74612 obtient un score CVSS de 10.0/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.49 %, ce qui la place devant 40.9 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, <=6.12.*, 6.6.152, 5.18, <41b96667d42b74bb4b137f1bb78b611a953c5943, 0, <cb6379feaaff11c4e1e79c26c745ffa23182768a, <=7.1.*, <5.18, <=6.6.*, 7.1.9, <=6.18.*, 6.1.184, 6.12.104, <2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139, 718a18a0c8a67f97781e40bdef7cdd055c430996, 6.18.45, <=*, <3205b0652a37255dbb7ca8f3d942c8d8aa677c21, <cdf745b7a777f87f51666e5d8f4c6fc279bcf54d, <0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5, 7.2) 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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