Medium [CVE-2026-89695] Linux kernel nfsd: Denial of Service via uncapped POSIX ACL count
This medium-severity Red Hat Linux advisory covers CVE-2026-89695.
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Summary
A flaw was found in the Linux kernel's Network File System Daemon (nfsd). The `nfsd4_decode_posixacl()` function, responsible for decoding POSIX Access Control Lists (ACLs), does not properly cap the entry count received from a client.
A remote attacker can exploit this by sending a specially crafted ACL with an excessively large entry count, leading to unbounded CPU usage during an O(n^2) sorting operation. This can result in a Denial of Service (DoS) for the affected server.
Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-606.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 19 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 19 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 19 minutes ago·verify at source
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