VulnerabilityPublished 21 Jan 2026Updated 2 Apr 2026

CVE-2026-1035: Red Hat build of Keycloak 26.4 · Time-of-check Time-of-use (TOCTOU) Race Condition

Affects Red Hat build of Keycloak 26.4Source CVE Database V5

Not known to be exploited · CVSS 3.1 Low.

Data as of 26 Oct 2026, 12:29 UTC

CVSS 3.1 base score

3.1Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 22% 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:N/I:L/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Red HatRed Hat build of Keycloak 26.4	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.4	Affected–	Fixed in–
Red HatRed Hat build of Keycloak 26.4.11	Affected–	Fixed in–
Red HatRed Hat JBoss Enterprise Application Platform 8	Affected–	Fixed in–
Red HatRed Hat JBoss Enterprise Application Platform Expansion Pack	Affected–	Fixed in–
Red HatRed Hat Single Sign-On 7	Affected–	Fixed in–

AI-suggested

To mitigate CVE-2026-1035, organizations should prioritize applying any official patches or updates released by Red Hat for Keycloak 26.4 that address this race condition. In the absence of immediate patches, administrators can implement concurrency controls such as synchronizing refresh token validation and update operations to ensure atomicity, preventing simultaneous refresh requests from bypassing single-use enforcement. Rate limiting refresh token requests per user or client can reduce the likelihood of concurrent exploitation. Monitoring and logging refresh token usage patterns for anomalies can help detect potential abuse. Additionally, reviewing and potentially relaxing strict refresh token rotation policies temporarily may reduce risk until a fix is applied. Employing multi-factor authentication and session management best practices can further limit the impact of compromised tokens. Finally, organizations should stay informed about updates from Red Hat and Keycloak communities regarding this vulnerability and apply recommended security advisories promptly.

Description

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.

Impact

The primary impact of CVE-2026-1035 is the undermining of refresh token rotation security mechanisms, which can lead to multiple access tokens being issued from a single refresh token. This compromises the integrity of the authentication process by allowing potential replay or session fixation attacks, where an attacker could gain unauthorized access or extend session lifetimes beyond intended limits. While confidentiality and availability are not directly affected, the integrity breach can facilitate lateral movement or privilege escalation within affected systems. Organizations relying on Keycloak for critical identity and access management may face increased risk of unauthorized access, especially in environments with high concurrency or automated token refresh workflows. The low CVSS score reflects the requirement for low privileges and network access, as well as the absence of user interaction, but the scope of affected systems is significant given Keycloak's widespread use in enterprise and cloud environments. Without mitigation, this vulnerability could be exploited in targeted attacks against organizations with strict token rotation policies, potentially impacting sensitive applications and services.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Apr 2026, 03:20 UTC

Technical details

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