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Advisory details: vulnrichment / CVE-2026-9704
Advisory ID vulnrichment/CVE-2026-9704
Aliases
Summary 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.
Status Published
Exploitability 0.5
Weighted Severity 0.0
Risk
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (1)
CWE-1284 Improper Validation of Specified Quantity in Input
System Score Found at
cvssv3.1 6.8
ssvc Track
Reference id Reference type URL
https://access.redhat.com/errata/RHSA-2026:30049
https://access.redhat.com/errata/RHSA-2026:30050
cpe:/a:redhat:build_keycloak:26.4::el9 Other https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:/a:redhat:build_keycloak:26.4::el9
cpe:/a:redhat:build_keycloak:26.6::el9 Other https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:/a:redhat:build_keycloak:26.6::el9
CVE-2026-9704 Advisory https://access.redhat.com/security/cve/CVE-2026-9704
RHSA-2026:25097 Advisory https://access.redhat.com/errata/RHSA-2026:25097
RHSA-2026:25098 Advisory https://access.redhat.com/errata/RHSA-2026:25098
show_bug.cgi?id=2481877 Bug https://bugzilla.redhat.com/show_bug.cgi?id=2481877
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N Found at None
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2026-05-27T15:29:17Z/ Found at None

Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2026-05-27T15:29:17Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/9xxx/CVE-2026-9704.json

Source Advisory: vulnrichment/CVE-2026-9704

View SSVC decision tree 
[{'Exploitation': 'none'},
 {'Automatable': 'no'},
 {'Technical Impact': 'total'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]