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VulnerabilityPublished Updated

CVE-2026-9704: Red Hat build of Keycloak 26.4 · Improper Validation of Specified Quantity in Input

Affects Red Hat build of Keycloak 26.4Source CVE Database V5

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Not known to be exploited · CVSS 6.8 Medium.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
6.8Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Red HatRed Hat build of Keycloak 26.4Affected–Fixed in–
Red HatRed Hat build of Keycloak 26.4Affected–Fixed in–
Red HatRed Hat build of Keycloak 26.4.13Affected–Fixed in–
Red HatRed Hat build of Keycloak 26.6Affected–Fixed in–
Red HatRed Hat build of Keycloak 26.6Affected–Fixed in–
Red HatRed Hat build of Keycloak 26.6.3Affected–Fixed in–

AI-suggested

Red Hat has released updated Keycloak 26.6.3 images that address this vulnerability. Users should upgrade to Red Hat build of Keycloak 26.6.3 or later to remediate this issue. Before applying the update, back up existing installations, including applications, configuration files, and databases. Patch status for version 26.4 is not explicitly stated; therefore, check the Red Hat advisory for the latest remediation guidance. No other specific mitigations are provided.

Description

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

References

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