GHSA-cpf7-j4cf-vqx4 CVE-2026-9803
Keycloak has an Out-of-bounds Read
Medium
Maven
- Severity
- 5.3 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.42%
- Chance of exploitation in the next 30 days. Higher than 36.08% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-125 Out-of-bounds Read
- Fix
26.6.3- Upgrade org.keycloak:keycloak-services to this version or later
Description
A flaw was found in Keycloak's ClientRegistrationAuth component. A remote unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with a malformed 'Authorization: Bearer' header to any client registration endpoint. This can lead to an ArrayIndexOutOfBoundsException, causing the server to return an HTTP 500 error and resulting in a Denial of Service (DoS) for the affected service.
Affected versions
Maven
| Package | Vulnerable | Fixed in |
|---|---|---|
| org.keycloak:keycloak-services | <= 26.4.7 |
No fix yet |
| org.keycloak:keycloak-services | >= 26.5.0, < 26.6.3 |
26.6.3 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
org.keycloak:keycloak-services Maven → 26.6.3
- maven
<dependency><groupId>org.keycloak</groupId><artifactId>keycloak-services</artifactId><version>26.6.3</version></dependency>- gradle
implementation("org.keycloak:keycloak-services:26.6.3")
Severity breakdown
CVSS 3.1 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Weakness
CWE-125: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How to prevent it
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.
- Architecture and Design: Use a language that provides appropriate memory abstractions.
References
Advisories
Packages
Other links
- github.com/keycloak/keycloak/issues/49433
- github.com/keycloak/keycloak/pull/49500
- github.com/keycloak/keycloak/pull/49617
- github.com/keycloak/keycloak/pull/49618
- github.com/keycloak/keycloak/commit/2b8692499e907e6205be0bd9c8a4da5d46f6ca30
- github.com/keycloak/keycloak/commit/3fc06909cc93eb5c4739a712fa350de625812e04
- github.com/keycloak/keycloak/commit/ef06df91d344c7e99fcb82987ef6adb854f30789
- access.redhat.com/errata/RHSA-2026:25097
- access.redhat.com/errata/RHSA-2026:25098
- access.redhat.com/errata/RHSA-2026:30049
- access.redhat.com/errata/RHSA-2026:30050
- access.redhat.com/security/cve/CVE-2026-9803
- bugzilla.redhat.com/show_bug.cgi
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-v3f7-2p4r-mwfw Keycloak vulnerable to cross-site scripting (xss) via case-insensitive uri validation bypass | High | Also affects org.keycloak:keycloak-services |
| GHSA-9jrw-8xf7-xqhq Keycloak vulnerable to information disclosure through arbitrary filesystem path probing | Medium | Also affects org.keycloak:keycloak-services |
| GHSA-w3p3-7cjg-vgfw Keycloak allows unauthorized access to resources via uma permission ticket bypass | Medium | Also affects org.keycloak:keycloak-services |
| GHSA-f5p5-6xmx-p252 Keycloak vulnerable to authorization bypass via incorrect uri comparison | High | Also affects org.keycloak:keycloak-services |
| GHSA-r7rc-c989-86g6 Keycloak: Attacker can re-enable and take over disabled clients via registration access token | Medium | Also affects org.keycloak:keycloak-services |
| GHSA-4gv3-mc9p-5wqc Keycloak: Unauthenticated account takeover via reset-credentials flow bypass | Critical | Also affects org.keycloak:keycloak-services |
| GHSA-6g26-7cx5-mrrg Keycloak: Information disclosure due to user profile permission bypass | Low | Also affects org.keycloak:keycloak-services |
| GHSA-v5g5-wwmp-jppw Keycloak has Insufficient Session Expiration | Medium | Also affects org.keycloak:keycloak-services |
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