VulnerabilityPublished 31 Jul 2026

CVE-2026-18217: Red Hat Build of Keycloak · Improper Input Validation

Affects Red Hat Build of KeycloakSource CVE Database V5

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Not known to be exploited · CVSS 3.4 Low.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

3.4Low

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 26% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:L/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: Required
Scope: Changed
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: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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 31 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 29 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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	Affected–	Fixed in–
Red HatRed Hat Data Grid 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

Red Hat currently does not provide a fix or mitigation that meets its criteria for ease of use, applicability, or stability. Users should be aware that mitigation options are limited or unavailable at this time. Monitoring Red Hat's advisory page for updates is recommended. No immediate action is mandated by Red Hat beyond awareness of the vulnerability and its conditions.

Description

CVE-2026-18217 is a vulnerability in the SAML protocol implementation of Red Hat Build of Keycloak. It arises when handling SAML authentication requests via the HTTP-Redirect binding with clients configured with wildcard redirect URLs. An attacker can craft requests with malicious parameters that get appended to legitimate responses, potentially causing some service providers to process attacker-supplied data and leading to users being logged into incorrect accounts. The vulnerability requires specific client configurations and downstream service providers that mishandle duplicate HTTP parameters. The severity is rated low with a CVSS score of 3.4. No official fix or mitigation meeting Red Hat's criteria is currently available.

Impact

Successful exploitation can lead to login cross-site request forgery (CSRF) or session swapping on affected service providers, causing users to be logged into incorrect accounts. The vulnerability does not impact confidentiality or availability but has a low integrity impact. Exploitation requires a network attacker with no privileges and user interaction. The issue arises from improper handling of query strings in SAML HTTP-Redirect binding responses, leading to parameter pollution.

Summary

This vulnerability in Red Hat Build of Keycloak involves improper input validation in the SAML HTTP-Redirect binding response handling. When a client uses a wildcard redirect URL, an attacker can inject malicious query parameters into the authentication request. Upon user authentication, Keycloak appends its legitimate SAML response to these attacker-controlled parameters without stripping or validating them. This parameter pollution can cause some service providers to process the attacker's data instead of the real login information, potentially resulting in login CSRF or session swapping attacks. Exploitation requires a specific client configuration and vulnerable downstream service providers. Red Hat rates the severity as Moderate but the CVSS score is 3.4 (low).

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What to do

Affected software

Description

AI analysisMachine-generated, updated 7 Aug 2026, 14:37 UTC

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