CVE-2025-2255 in Community Edition
Summary
by MITRE • 03/27/2025
An issue has been discovered in Gitlab EE/CE for AppSec affecting all versions from 13.5.0 before 17.8.6, 17.9 before 17.9.3, and 17.10 before 17.10.1. Certain error messages could allow Cross-Site Scripting attacks (XSS). for AppSec.
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Analysis
by VulDB Data Team • 08/13/2025
This vulnerability exists in GitLab Enterprise Edition and Community Edition applications within the Application Security module, affecting versions from 13.5.0 through 17.8.5, 17.9.0 through 17.9.2, and 17.10.0 through 17.10.0. The flaw manifests in error message handling mechanisms that fail to properly sanitize user input before rendering responses to web clients. This represents a classic cross-site scripting vulnerability where malicious actors can inject malicious scripts into error messages that are subsequently executed in the context of other users' browsers. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws in software applications. From an operational perspective, this vulnerability poses significant risk to organizations relying on GitLab's security features, as attackers could exploit this weakness to execute arbitrary code in users' browsers, potentially leading to session hijacking, data theft, or privilege escalation within the GitLab environment.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding within GitLab's error handling subsystem. When GitLab encounters certain security-related errors during application security operations, it generates error messages that include raw user input without proper sanitization or HTML escaping. This allows attackers to craft malicious payloads that, when processed by the application, get rendered as executable JavaScript code in victim browsers. The vulnerability is particularly concerning because it occurs within the AppSec module, which is designed to protect applications from security threats, making it a prime target for exploitation. The specific versions affected indicate this is a long-standing issue that was addressed through multiple patch releases, suggesting the flaw has been present for several years within the application's codebase.
Attackers can leverage this vulnerability by crafting inputs that trigger specific error conditions within GitLab's security modules, then injecting malicious scripts that will execute when other users view the resulting error messages. The attack vector aligns with ATT&CK technique T1531 which focuses on use of valid accounts to gain access to systems, but in this case the exploitation occurs through the injection of malicious content rather than credential theft. The impact extends beyond simple XSS execution as it can enable more sophisticated attacks such as cookie theft, session manipulation, or even redirection to malicious sites. Organizations using GitLab's Application Security features are particularly at risk since these modules are often used in production environments where sensitive security information is handled. The vulnerability demonstrates a critical gap in the application's security architecture where error handling does not properly separate data from code execution contexts.
Organizations should immediately apply the relevant patches to versions 17.8.6, 17.9.3, and 17.10.1 to remediate this vulnerability. The mitigation strategy should include comprehensive input validation across all error handling paths within the application security components. System administrators should also implement additional monitoring to detect unusual error message patterns that might indicate exploitation attempts. Network-level protections such as web application firewalls can provide additional defense-in-depth measures, though these should not be relied upon as the sole remediation. The fix implemented by GitLab likely involves implementing proper HTML escaping and input sanitization for all error messages generated within the AppSec module, ensuring that user-supplied data cannot be interpreted as executable code. Security teams should conduct thorough testing to verify that the patch does not introduce regressions in legitimate error handling functionality while maintaining the security improvements. This vulnerability underscores the importance of secure error handling practices and demonstrates how seemingly innocuous error message generation can create significant security risks in application security tools.