CVE-2026-89550Network attack vector

Authenticated server crash via truncated krb5 token

Published Sep 11, 2026 · Updated Sep 11, 2026

Denial of service in Linux kernel SUNRPC allows remote authenticated users to crash an NFS server via a short RFC 4121 krb5 token. svcauth_gss_unwrap_priv() checks only the token's upper length bound, so gss_krb5_unwrap_v2() reads beyond a truncated header and rotate_left() can divide by zero. Exploitation requires an established krb5 v2 RPCSEC_GSS context and interrupts the affected server.

CVSS severityUnavailable
Unscored
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Linux kernel SUNRPC allows remote authenticated users to crash an NFS server via a short RFC 4121 krb5 token. svcauth_gss_unwrap_priv() checks only the token's upper length bound, so gss_krb5_unwrap_v2() reads beyond a truncated header and rotate_left() can divide by zero. Exploitation requires an established krb5 v2 RPCSEC_GSS context and interrupts the affected server.

The record

CVE
CVE-2026-89550
Published
Sep 11, 2026
Updated
Sep 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.18
  2. Affected versionversion=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <2eed1e6a976a44015c3ee78841fe336796e2b21c
  3. Affected versionversion=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <a919c5c88769cf8fb3ec071e6078d830bf512489
  4. Affected versionversion=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <dd6afc6cab8c5d387d1ed2f069562ef7bdadd651
  5. Affected versionversion=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <de942dd8c2c8358bcad04ce44271954c48924423

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.18; version=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <2eed1e6a976a44015c3ee78841fe336796e2b21c; version=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <a919c5c88769cf8fb3ec071e6078d830bf512489; version=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <dd6afc6cab8c5d387d1ed2f069562ef7bdadd651; version=7c9fdcfb1b64c47ed618c103b617af3f86e1239c <de942dd8c2c8358bcad04ce44271954c48924423

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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