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CVE-2026-63920

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.1 · Élevée
EPSS 0.2%
Linux•Linux•Versions : <=6.1.*, <eb18a1b1644e4cad978df2131e2bb9a2e6886992, <=7.0.*, <=6.12.*, 2.6.12, 6.12.93, 0, 6.18.35, <81394827dfb72772c50d0ae3bdfa094428a5d76d, 6.1.176, <2.6.12, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 5.15.210, <=5.10.*, <=6.6.*, <dd433671fef381fdaf7b530c631e6b782d66e224, <931b4a1f13408c2507719890f78f7227c34a0282, <08464413e628803bd10cb1df68d0138665f2f885, 7.1, <=6.18.*, <0d330eff318c0f44d4fb0ad2c2aef38f87f24c90, 7.0.12, <=*, <a29768d56eb3798c052ad3281b05596e695a17af, <=5.15.*, 6.6.143, 5.10.259, <a35daeabb433686234b010ebf7b53778dbd6c9b8

Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: validate extension header length before copying to cmsg ip6_datagram_recv_specific_ctl() builds IPV6_{HOPOPTS,DSTOPTS,RTHDR} cmsgs (and their IPV6_2292* legacy counterparts) by trusting the on-wire hdrlen byte (ptr[1]) when computing the put_cmsg() length. The length was validated only at parse time (ipv6_parse_hopopts(), etc.). An nftables payload-write expression can rewrite hdrlen after parsing and before the skb reaches recvmsg; the write itself is in-bounds but put_cmsg() then reads up to ((hdrlen+1) << 3) = 2040 bytes from an 8-byte header. nftables is reachable from an unprivileged user namespace, so this is an unprivileged slab-out-of-bounds read: BUG: KASAN: slab-out-of-bounds in put_cmsg+0x3ac/0x540 put_cmsg+0x3ac/0x540 udpv6_recvmsg+0xca0/0x1250 sock_recvmsg+0xdf/0x190 ____sys_recvmsg+0x1b1/0x620 Add ipv6_get_exthdr_len() which validates that at least two bytes are accessible before reading the hdrlen field, then checks the computed length against skb_tail_pointer(skb), returning 0 on failure. Extension headers are kept in the linear skb area by pskb_may_pull() during input, so skb_tail_pointer() is the correct bound. Use ipv6_get_exthdr_len() at all non-AH call sites: the five standalone cmsg blocks (HbH, 2292HbH, 2292DSTOPTS x2, 2292RTHDR) and the three standard cases in the extension-header walk loop (DSTOPTS, ROUTING, default). AH retains an inline bounds check because its length formula differs ((ptr[1]+2)<<2). The walk loop also gets a pre-read bounds check at the top to validate ptr before any case accesses ptr[0] or ptr[1]. When the walk loop detects a corrupted header, return from the function instead of continuing to process later socket options.

Gravité et risque d'exploitation

CVE-2026-63920 obtient un score CVSS de 7.1/10, 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 6.1 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, <eb18a1b1644e4cad978df2131e2bb9a2e6886992, <=7.0.*, <=6.12.*, 2.6.12, 6.12.93, 0, 6.18.35, <81394827dfb72772c50d0ae3bdfa094428a5d76d, 6.1.176, <2.6.12, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 5.15.210, <=5.10.*, <=6.6.*, <dd433671fef381fdaf7b530c631e6b782d66e224, <931b4a1f13408c2507719890f78f7227c34a0282, <08464413e628803bd10cb1df68d0138665f2f885, 7.1, <=6.18.*, <0d330eff318c0f44d4fb0ad2c2aef38f87f24c90, 7.0.12, <=*, <a29768d56eb3798c052ad3281b05596e695a17af, <=5.15.*, 6.6.143, 5.10.259, <a35daeabb433686234b010ebf7b53778dbd6c9b8) 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

Rechercher une autre CVE