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CVE-2026-63984

Vulnérabilité critique dans Linux (Linux)

CVSS 9.8 · Critique
EPSS 0.5%
Linux•Linux•Versions : <=6.1.*, <=7.0.*, <=6.12.*, 6.12.93, <c0487a9c1e116cf349e2d1f302d9019670460858, <6fe1cb312038516cb4d9fa089d700af7059f1a64, 0, 6.18.35, <fd238c51b0fa5390cceca9f1ac5a9ffda8063eed, <9d5e7a46a9f6d8f503b41bfefef70659845f1679, 6.1.176, 5.15.210, <5.7, <=5.10.*, <=6.6.*, 7.1, <=6.18.*, 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3, <3618b34942b76471d044369bfd30d58c39068bf1, 5.7, 7.0.12, <=*, <=5.15.*, 6.6.143, <75b3680047bf09af8e7e471a7a6ddf2ce5847f56, <de02fc049352af5a9595f015511222d0a85c326b, <97e06791368c01f0ad2a4b3269c2abe19485ca32, 5.10.259

Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress() ipv6_rpl_srh_decompress() computes: outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3); hdrlen is __u8. For n >= 127 the result exceeds 255 and silently truncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16): (128 * 16) >> 3 = 256, truncated to 0 as __u8 The caller in ipv6_rpl_srh_rcv() then places the compressed header at buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8, but the decompressed region occupies buf[0..2055] (8-byte header plus 128 full addresses). The compressed header overlaps the decompressed data, and ipv6_rpl_srh_compress() writes into this overlap, corrupting the routing header of the forwarded packet. The existing guard at exthdrs.c:546 checks (n + 1) > 255, which prevents n+1 from overflowing unsigned char (the segments_left field), but does not prevent the computed hdrlen from overflowing __u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not fit. Tighten the bound to (n + 1) > 127. This caps n at 126, giving hdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed header then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly past the decompressed region (buf[0..2039]). No overlap. 127 segments is well beyond any realistic RPL deployment.

Gravité et risque d'exploitation

CVE-2026-63984 obtient un score CVSS de 9.8/10, soit une gravité critique. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.51 %, ce qui la place devant 42.6 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, <=7.0.*, <=6.12.*, 6.12.93, <c0487a9c1e116cf349e2d1f302d9019670460858, <6fe1cb312038516cb4d9fa089d700af7059f1a64, 0, 6.18.35, <fd238c51b0fa5390cceca9f1ac5a9ffda8063eed, <9d5e7a46a9f6d8f503b41bfefef70659845f1679, 6.1.176, 5.15.210, <5.7, <=5.10.*, <=6.6.*, 7.1, <=6.18.*, 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3, <3618b34942b76471d044369bfd30d58c39068bf1, 5.7, 7.0.12, <=*, <=5.15.*, 6.6.143, <75b3680047bf09af8e7e471a7a6ddf2ce5847f56, <de02fc049352af5a9595f015511222d0a85c326b, <97e06791368c01f0ad2a4b3269c2abe19485ca32, 5.10.259) 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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