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CVE-2021-47506

Vulnérabilité critique dans Linux (Linux)

CVSS 9.8 · Critique
EPSS 0.8%
Linux•Linux•Versions : <33645d3e22720cac1e4548f8fef57bf0649536ee, 5.16, 5.15.8, 4.9.294, 0, <2becaa990b93cbd2928292c0b669d3abb6cf06d4, 4.4.296, 5.4.168, <eeb0711801f5e19ef654371b627682aed3b11373, <=4.9.*, <=5.10.*, <=4.14.*, <148c816f10fd11df27ca6a9b3238cdd42fa72cd3, <548ec0805c399c65ed66c6641be467f717833ab5, <348714018139c39533c55661a0c7c990671396b4, <=5.4.*, 5.10.85, <e0759696de6851d7536efddfdd2dfed4c4df1f09, <=4.19.*, 4.19.222, <=4.4.*, <=*, <=5.15.*, <3.17, dff1399f8addf7129c49bb2227469da79cc30b47, 3.17, <04a8d07f3d58308b92630045560799a3faa3ebce, 4.14.259

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease. A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.

Gravité et risque d'exploitation

CVE-2021-47506 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 0.78 %, ce qui la place devant 55.3 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <33645d3e22720cac1e4548f8fef57bf0649536ee, 5.16, 5.15.8, 4.9.294, 0, <2becaa990b93cbd2928292c0b669d3abb6cf06d4, 4.4.296, 5.4.168, <eeb0711801f5e19ef654371b627682aed3b11373, <=4.9.*, <=5.10.*, <=4.14.*, <148c816f10fd11df27ca6a9b3238cdd42fa72cd3, <548ec0805c399c65ed66c6641be467f717833ab5, <348714018139c39533c55661a0c7c990671396b4, <=5.4.*, 5.10.85, <e0759696de6851d7536efddfdd2dfed4c4df1f09, <=4.19.*, 4.19.222, <=4.4.*, <=*, <=5.15.*, <3.17, dff1399f8addf7129c49bb2227469da79cc30b47, 3.17, <04a8d07f3d58308b92630045560799a3faa3ebce, 4.14.259) 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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