A Linux kernel NFS server TOCTOU allows remote NFS clients to bypass append-only checks and truncate files — widespread kernel component with high data-loss impact.
CVE-2026-89713
NFS server TOCTOU lets remote clients truncate append-only files
Is CVE-2026-89713 being exploited?
Not confirmed. CVE-2026-89713 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.60% probability of exploitation in the next 30 days.
How severe is CVE-2026-89713?
CVE-2026-89713 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-89713?
Yes. A fix has been recorded for CVE-2026-89713. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-89713 affect?
CVE-2026-89713 affects Linux kernel (nfsd) on NFS servers, Linux distributions with unpatched kernels. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-89713?
Apply vendor/kernel security updates to patched kernel immediately; restrict NFS client access until patched.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote NFS client can cause unauthorized truncation of append-only files (data loss/integrity breach) via TOCTOU in nfsd_setattr.
Immediate action required
- affected>= 783112f7401ff449d979530209b3f6c2594fdb4e and < 3afa17d93ba8c925f49370c816c6dae5112d8c24
- affected>= 783112f7401ff449d979530209b3f6c2594fdb4e and < d8352da196349182e1afd5a93308256cddc0a97d
- affected>= 783112f7401ff449d979530209b3f6c2594fdb4e and < 44086254479035de42ca3d286ecf25521d4e6325
- affected>= 783112f7401ff449d979530209b3f6c2594fdb4e and < b778e0e0a16759f22a70579c3cf8d254a40d4a7f
- affected604a3c407026d6162d15300478e63f901e435efc
- affectedcc4d5dc73841b98d33cdfb9822d70b0aac4beca5
- affected3ee4f442e5b37a537297b812557b1163f96b5399
- affecteda3c6cbc4eac4473ed5461d5faae2794d3e5c0e44
- affected982898d7f97a35447403c3fcecc0d96c646ce101
- affected>= 3.2.89 and < 3.3
- affected>= 3.16.44 and < 3.17
- affected>= 4.4.53 and < 4.5
- affected>= 4.9.14 and < 4.10
- affected>= 4.10.2 and < 4.11
- affected4.11
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.