Summary
Rancher Fleet has Unauthenticated Webhook: Regex Injection via Unsanitized Repository URL Components
Full technical description
Workarounds
If you can't upgrade to a fixed version, please make sure to only enable webhooks with a shared secret.
Credits
This security issue was reported by the following collaborators according to our responsible disclosure policy:
- Radisauskas Arnoldas from NATO and the NATO Cyber Security Centre (NCSC).
References
If you have any questions or comments about this advisory:
- Reach out to the SUSE Rancher Security team for security related inquiries.
- Open an issue in the Rancher repository.
- Verify with our support matrix and product support lifecycle.
Impact
A vulnerability has been identified in Fleet when the webhook endpoint is configured without a secret; an attacker can forge webhook requests. The attacker doesn't need to know the specific repository or path configured in the GitRepo resource to make Fleet process these requests.
An attacker can exploit this vulnerability to cause the following impacts:
- Trigger continuous repository re-cloning, which increases network traffic and can deplete resources on the management cluster.
- Downgrade running services to any historical revision available in the remote Git repository. This risk applies if the attacker has read access to the target Git repository and knows its configured path.
Please consult the associated MITRE ATT&CK - Technique - T1499.004: Endpoint Denial of Service for further information about this category of attack.
CVE-2026-44937 has a CVSS score of 7.5 (High). The vector is network-reachable, no 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 (0.15.2, 0.14.6, 0.13.11, 0.12.15); 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.
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To resolve this vulnerability, upgrade Fleet to a patched version. This upgrade version escapes the URL and path to the remote repository received from webhooks, which prevents regular expressions from being used as a replacement for the URL and path.
Patched versions of Fleet include releases v0.15.2, v0.14.6, 0.13.11, and v0.12.15.
Frequently Asked Questions
- What is CVE-2026-44937? CVE-2026-44937 is a high-severity security vulnerability in github.com/rancher/fleet (go), affecting versions >= 0.15.0, < 0.15.2. It is fixed in 0.15.2, 0.14.6, 0.13.11, 0.12.15.
- How severe is CVE-2026-44937? CVE-2026-44937 has a CVSS score of 7.5 (High). 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 github.com/rancher/fleet are affected by CVE-2026-44937? github.com/rancher/fleet (go) versions >= 0.15.0, < 0.15.2 is affected.
- Is there a fix for CVE-2026-44937? Yes. CVE-2026-44937 is fixed in 0.15.2, 0.14.6, 0.13.11, 0.12.15. Upgrade to this version or later.
- Is CVE-2026-44937 exploitable, and should I be worried? Whether CVE-2026-44937 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-2026-44937 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-2026-44937?
- Upgrade
github.com/rancher/fleetto 0.15.2 or later - Upgrade
github.com/rancher/fleetto 0.14.6 or later - Upgrade
github.com/rancher/fleetto 0.13.11 or later - Upgrade
github.com/rancher/fleetto 0.12.15 or later
- Upgrade