Summary
Weblate has a Server-Side Request Forgery issue
Workarounds
Removing Mercurial from VCS_BACKENDS avoids this vulnerability, as the Git backend is not affected. The Git backend was already configured to block the file protocol and does not expose the HTTP response content in the error message.
References
Thanks to Jason Marcello for responsible disclosure.
Impact
The Create Component functionality in Weblate allows authorized users to add new translation components by specifying both a version control system and a source code repository URL to pull from. However, the repository URL field is not validated or sanitized, allowing an attacker to supply arbitrary protocols, hostnames, and IP addresses, including localhost, internal network addresses, and local filenames.
When the Mercurial version control system is selected, Weblate exposes the full server-side HTTP response for the provided URL. This effectively creates a server-side request forgery (SSRF) primitive that can probe internal services and return their contents. In addition to accessing internal HTTP endpoints, the behavior also enables local file enumeration by attempting file:// requests. While file contents may not always be returned, the application’s error messages clearly differentiate between files that exist and files that do not, revealing information about the server’s filesystem layout.
In cloud environments, this behavior is particularly dangerous, as internal-only endpoints such as cloud metadata services may be accessible, potentially leading to credential disclosure and full environment compromise.
A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.
CVE-2025-66407 has a CVSS score of 5.0 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.15); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
This has been addressed in the Weblate 5.15 release.
Frequently Asked Questions
- What is CVE-2025-66407? CVE-2025-66407 is a medium-severity cross-site request forgery (CSRF) vulnerability in Weblate (pip), affecting versions < 5.15. It is fixed in 5.15. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
- How severe is CVE-2025-66407? CVE-2025-66407 has a CVSS score of 5.0 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of Weblate are affected by CVE-2025-66407? Weblate (pip) versions < 5.15 is affected.
- Is there a fix for CVE-2025-66407? Yes. CVE-2025-66407 is fixed in 5.15. Upgrade to this version or later.
- Is CVE-2025-66407 exploitable, and should I be worried? Whether CVE-2025-66407 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-66407 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-66407? Upgrade
Weblateto 5.15 or later.