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Full vulnerability report · 2026
CVE-2026-15571High confidence

Keycloak-services: keycloak-services: predictable account-linking hash enables account takeover via malicious oidc client

Red Hat · Red Hat build of Keycloak 26.6

Official source article: Red Hat RHSA-2026:56523 ↗. Check the applicable product and release in the original source.

7.3HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.43% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Red Hat Red Hat build of Keycloak 26.6 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-15571 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitykeycloak-services: keycloak-services: Predictable account-linking hash enables account takeover via malicious OIDC client
10 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • rhbk/keycloak-operator-bundle@sha256:59dc8a796829d2ffd605425348c9801ae38823da3269006a1fcc7d013a41eb30_amd64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:44d03f041fd1760001776e4e08d1f4716da4dd00d50476c91206b6db4934147d_arm64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:80434d4628a04d1c82ea21c0ed0b0e4122823686cab030afcd77ec485c5b7d18_s390x as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:c1ce5e79c69440caa9ccc761167b068e259cd126dfbdde28e36ae590c2bf60f5_amd64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:c32f09e3b7c212e7fd6b4a9b7b5857e4fd18d4416e5d256ca99299377edeb05e_ppc64le as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:2bf0b7db309d716f5ced722869f59a7307aaff57e9c223a1e594145a560c8178_amd64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:413763d73d26774b9278d71dd2eea226bedaeac307ee146736a7ffbf7f613f0d_arm64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:9c2a11371c3edb48bb24413a0aa60ff01efcdd2c1af45b07905f216e4648675f_ppc64le as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:e5a8533ccec075ff65f3447fd186a14069452e4446331a8f95530a2a86cb52a7_s390x as a component of Red Hat build of Keycloak 26.6
  • Red Hat build of Keycloak 26.6.6
Summary
A flaw was found in the legacy client-initiated account-linking endpoint of Keycloak, a widely used open-source identity and access management solution. The mechanism used to protect the account-linking process from unauthorized requests relies on a hash that can be predicted by a malicious OIDC client. By tricking a user into authenticating, an attacker-controlled client can forge a valid linking URL to connect the victim's account to an attacker's external identity. This results in a full account takeover, allowing the attacker to log in as the victim.
Remediation
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-61238

No EUVD known-exploited evidence

A flaw was found in the legacy client-initiated account-linking endpoint of Keycloak, a widely used open-source identity and access management solution. The mechanism used to protect the account-linking process from unauthorized requests relies on a hash that can be predicted by a malicious OIDC client. By tricking a user into authenticating, an attacker-controlled client can forge a valid linking URL to connect the victim's account to an attacker's external identity. This results in a full account takeover, allowing the attacker to log in as the victim.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.3 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

A flaw was found in the legacy client-initiated account-linking endpoint of Keycloak, a widely used open-source identity and access management solution. The mechanism used to protect the account-linking process from unauthorized requests relies on a hash that can be predicted by a malicious OIDC client. By tricking a user into authenticating, an attacker-controlled client can forge a valid linking URL to connect the victim's account to an attacker's external identity. This results in a full account takeover, allowing the attacker to log in as the victim.

What

A flaw was found in the legacy client-initiated account-linking endpoint of Keycloak, a widely used open-source identity and access management solution. The mechanism used to protect the account-linking process from unauthorized requests relies on a hash that can be predicted by a malicious OIDC client. By tricking a user into authenticating, an attacker-controlled client can forge a valid linking URL to connect the victim's account to an attacker's external identity. This results in a full account takeover, allowing the attacker to log in as the victim.

Why

A number or object is predictable based on observations that the attacker can make about the state of the system or network, such as time, process ID, etc.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may bypass an access boundary or take over an account.

What

A flaw was found in the legacy client-initiated account-linking endpoint of Keycloak, a widely used open-source identity and access management solution. The mechanism used to protect the account-linking process from unauthorized requests relies on a hash that can be predicted by a malicious OIDC client. By tricking a user into authenticating, an attacker-controlled client can forge a valid linking URL to connect the victim's account to an attacker's external identity. This results in a full account takeover, allowing the attacker to log in as the victim.

Why

A number or object is predictable based on observations that the attacker can make about the state of the system or network, such as time, process ID, etc.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may bypass an access boundary or take over an account.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Predictable from Observable State → bypass an access boundary or take over an account
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
User interaction
Required interaction required
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-341 ↗

CWE-341: Predictable from Observable State. A number or object is predictable based on observations that the attacker can make about the state of the system or network, such as time, process ID, etc.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
NetworkCWE-341
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-61238Official EUVD mapping

A flaw was found in the legacy client-initiated account-linking endpoint of Keycloak, a widely used open-source identity and access management solution. The mechanism used to protect the account-linking process from unauthorized requests relies on a hash that can be predicted by a malicious OIDC client. By tricking a user into authenticating, an attacker-controlled client can forge a valid linking URL to connect the victim's account to an attacker's external identity. This results in a full account takeover, allowing the attacker to log in as the victim.

Official EUVD record ↗
BSI · German · WID-SEC-2026-2915Keycloak: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Keycloak ausnutzen, um Sicherheitsvorkehrungen zu umgehen und dadurch Benutzerkonten zu übernehmen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1078Multiples vulnérabilités dans Keycloak

De multiples vulnérabilités ont été découvertes dans Keycloak. Elles permettent à un attaquant de provoquer un contournement de la politique de sécurité et un problème de sécurité non spécifié par l'éditeur. Le CERT-FR a connaissance d'une preuve de concept publique pour la vulnérabilité CVE-2026-18963 qui permet à un attaquant non authentifié de prendre le contrôle d'un compte dont il connait l'identifiant.

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0326Kwetsbaarheden verholpen in Keycloak

A critical vulnerability in Keycloak's legacy client-initiated account-linking endpoint allows attackers to predict security hashes and forge linking URLs, enabling unauthorized account linking and full account takeover.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Red Hat build of Keycloak 26.6: patch: 26.6-12, patch: 26.6.6-1
Fixed
Action
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 18 Aug 2026 · Last source change 20 Aug 2026, 14:07 UTC · CWE-341 · Predictable from Observable State

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-23
European sourceENISA EUVD · EUVD-2026-61238
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD awaiting enrichment

Missing structured fields: affected versions. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
    Before
    no BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    See the vendor and CVE records for the affected range. · Fixed: 26.6-12 < *; 26.6.6-1 < *
    After
    See the vendor and CVE records for the affected range. · Fixed: 26.6.6-1 < *; 26.6-12 < *
    CNA ↗
  3. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-61238↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference · Red Hat RHSA-2026:56523↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-15571 · cve.blacktree.nl