What’s Vulnerable › Vulnerabilities

CVE-2021-46952: NFS: fs_context: validate UDP retrans to prevent shift out-of-bounds

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2024-02-27 · updated 2026-06-17
• Weakness: CWE-125

Description

In the Linux kernel, the following vulnerability has been resolved: NFS: fs_context: validate UDP retrans to prevent shift out-of-bounds Fix shift out-of-bounds in xprt_calc_majortimeo(). This is caused by a garbage timeout (retrans) mount option being passed to nfs mount, in this case from syzkaller. If the protocol is XPRT_TRANSPORT_UDP, then 'retrans' is a shift value for a 64-bit long integer, so 'retrans' cannot be >= 64. If it is >= 64, fail the mount and return an error.

Affected products

• Linux kernel: from 5.6.0 before 5.10.36; from 5.11.0 before 5.11.20; from 5.12.0 before 5.12.3 — fixed in 5.10.36, 5.11.20, 5.12.3

How to fix

Upgrade to a fixed version: Linux kernel 5.10.36, 5.11.20, 5.12.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/2f3380121d49e829fb73ba86240c181bc32ad897
• https://git.kernel.org/stable/c/3d0163821c035040a46d816a42c0780f0f0a30a8
• https://git.kernel.org/stable/c/96fa26b74cdcf9f5c98996bf36bec9fb5b19ffe2
• https://git.kernel.org/stable/c/c09f11ef35955785f92369e25819bf0629df2e59
• https://git.kernel.org/stable/c/2f3380121d49e829fb73ba86240c181bc32ad897
• https://git.kernel.org/stable/c/3d0163821c035040a46d816a42c0780f0f0a30a8
• https://git.kernel.org/stable/c/96fa26b74cdcf9f5c98996bf36bec9fb5b19ffe2
• https://git.kernel.org/stable/c/c09f11ef35955785f92369e25819bf0629df2e59

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