Staging Environment: Content and features may be unstable or change without notice.
Advisory details: github_osv / GHSA-h4wv-g838-66g3
Advisory ID github_osv/GHSA-h4wv-g838-66g3
Aliases CVE-2026-4634
Summary Keycloak: Application-Level DoS via Scope Processing A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.
Status Published
Exploitability 0.5
Weighted Severity 6.8
Risk 3.4
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (1)
CWE-1050 Excessive Platform Resource Consumption within a Loop
System Score Found at
cvssv3.1 7.5 https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-h4wv-g838-66g3/GHSA-h4wv-g838-66g3.json
generic_textual HIGH
Reference id Reference type URL
https://access.redhat.com/errata/RHSA-2026:6475
https://access.redhat.com/errata/RHSA-2026:6476
https://access.redhat.com/security/cve/CVE-2026-4634
https://bugzilla.redhat.com/show_bug.cgi?id=2450250
https://github.com/keycloak/keycloak
https://github.com/keycloak/keycloak/commit/b455ee4f28abb6f2120aff72fd179589cc5267a0
https://github.com/keycloak/keycloak/issues/47716
CVE-2026-4634 https://nvd.nist.gov/vuln/detail/CVE-2026-4634
RHSA-2026:6477 Advisory https://access.redhat.com/errata/RHSA-2026:6477
RHSA-2026:6478 Advisory https://access.redhat.com/errata/RHSA-2026:6478
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:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-h4wv-g838-66g3/GHSA-h4wv-g838-66g3.json
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:Y/T:P/P:M/B:A/M:M/D:T/2026-04-03T17:22:51Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/4xxx/CVE-2026-4634.json

Source Advisory: vulnrichment/CVE-2026-4634

View SSVC decision tree 
[{'Exploitation': 'none'},
 {'Automatable': 'yes'},
 {'Technical Impact': 'partial'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]

Vector: SSVCv2/E:N/A:Y/T:P/P:M/B:A/M:M/D:T/2026-04-03T17:22:51Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/4xxx/CVE-2026-4634.json

Source Advisory: vulnrichment/CVE-2026-4634

View SSVC decision tree 
[{'Exploitation': 'none'},
 {'Automatable': 'yes'},
 {'Technical Impact': 'partial'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]