Red Hat Keycloak Refresh Token TokenManager toctou

Summaryinfo

A vulnerability classified as problematic has been found in Red Hat Keycloak. Affected by this issue is the function TokenManager of the component Refresh Token Handler. This manipulation causes toctou. This vulnerability is registered as CVE-2026-1035. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability classified as problematic was found in Red Hat Keycloak (version now known). Affected by this vulnerability is the function TokenManager of the component Refresh Token Handler. The manipulation with an unknown input leads to a toctou vulnerability. The CWE definition for the vulnerability is CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. As an impact it is known to affect integrity. The summary by CVE is:

A flaw was found in the Keycloak server during refresh token processing, specifically in the TokenManager class responsible for enforcing refresh token reuse policies. When strict refresh token rotation is enabled, the validation and update of refresh token usage are not performed atomically. This allows concurrent refresh requests to bypass single-use enforcement and issue multiple access tokens from the same refresh token. As a result, Keycloak’s refresh token rotation hardening can be undermined.

The advisory is shared at access.redhat.com. This vulnerability is known as CVE-2026-1035 since 01/16/2026. The exploitation appears to be difficult. The attack can be launched remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 02/04/2026).

The vulnerability scanner Nessus provides a plugin with the ID 297730 (Linux Distros Unpatched Vulnerability : CVE-2026-1035), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at CNNVD (CNNVD-202601-3440), Tenable (297730) and CERT Bund (WID-SEC-2026-0197). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• Open Source Keycloak

Productinfo

Vendor

• Red Hat

Name

• Keycloak

License

• open-source

Website

• Vendor: https://www.redhat.com/

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion