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CVE-2026-89551

Vulnérabilité critique dans Linux (Linux)

CVSS 9.8 · Critique
EPSS 0.5%
Linux•Linux•Versions : <=6.1.*, <=6.12.*, 5.15.221, 5.10.270, 0, <3.9, 7.2.4, <3f491306dcb673ff5e78e1044ba450c58978774e, 6.1.188, 4c190e2f913f038c9c91ee63b59cd037260ba353, <a924ac4c78afab71bf82641afa3b62e0c4a8b55e, <=5.10.*, <=6.6.*, <fa16bbe987b47e771e52eeb1b4540f18d92496ac, 6.6.157, <a3d77bcd974b8625d16bddf448cb3a1b5e37049c, <4bf59cb0ea5b0ddfbc46a1dc2fa78fc8b9986ce4, <=6.18.*, 7.3, <=7.2.*, <ad0cce80d4af2f74674e8b635d97aa3880e83da8, <=*, <=5.15.*, <e6267cccd7b05cc514e57f2160aa8db85f5c2701, 6.18.50, 6.12.109, <85e9602650e9df07190abe817cee3b4d9bc3df17, 3.9

Description

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: xdr_buf_trim: clamp buf->len to avoid underflow xdr_buf_trim() trims `len` bytes from the tail of an xdr_buf by walking the tail, pages, and head iovecs. Each per-section step uses min_t() so it never removes more bytes than that section holds, but the final accounting at the fix_len label subtracts the total bytes actually consumed from buf->len without any clamp: fix_len: buf->len -= (len - trim); When the caller has set buf->len to a value smaller than the sum of the iov_lens, (len - trim) can exceed buf->len and the unsigned subtraction wraps to near UINT_MAX. gss_krb5_unwrap_v2() reaches xdr_buf_trim() in exactly that state: buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip; buf->len = len - (GSS_KRB5_TOK_HDR_LEN + headskip); xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip); buf->len is a small wire-derived value while the iov_lens are at page scale, so the per-section loops legitimately consume far more bytes than buf->len records. The wrapped buf->len then propagates as the authoritative stream bound into every downstream XDR decoder. Fix by clamping the decrement so buf->len bottoms out at zero: buf->len -= min_t(unsigned int, buf->len, len - trim); On the normal path where the iov_lens sum to buf->len, (len - trim) is always <= buf->len and the result is identical to before. No callers change behavior outside the underflow case.

Gravité et risque d'exploitation

CVE-2026-89551 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.*, <=6.12.*, 5.15.221, 5.10.270, 0, <3.9, 7.2.4, <3f491306dcb673ff5e78e1044ba450c58978774e, 6.1.188, 4c190e2f913f038c9c91ee63b59cd037260ba353, <a924ac4c78afab71bf82641afa3b62e0c4a8b55e, <=5.10.*, <=6.6.*, <fa16bbe987b47e771e52eeb1b4540f18d92496ac, 6.6.157, <a3d77bcd974b8625d16bddf448cb3a1b5e37049c, <4bf59cb0ea5b0ddfbc46a1dc2fa78fc8b9986ce4, <=6.18.*, 7.3, <=7.2.*, <ad0cce80d4af2f74674e8b635d97aa3880e83da8, <=*, <=5.15.*, <e6267cccd7b05cc514e57f2160aa8db85f5c2701, 6.18.50, 6.12.109, <85e9602650e9df07190abe817cee3b4d9bc3df17, 3.9) 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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