Summary
rclone: WebDAV Credentials Survive a Same-Host HTTPS-to-HTTP Redirect
1. Summary
WebDAV's default redirect handling can replay Basic authorization and configured Cookie headers over plaintext HTTP after a same-host HTTPS-to-HTTP redirect. This was reproduced through the real backend. Unlike the low-impact STS token in rclone's published S3 redirect advisory, Basic passwords and session cookies are complete reusable credentials, supporting a High rating when they grant normal WebDAV read/write access.
The credible threat requires a legitimate endpoint, gateway, or accelerator to emit an unsafe redirect and an adjacent/on-path actor to observe the plaintext hop. A report should not rely on a malicious original WebDAV endpoint because that endpoint already receives the credentials.
2. Affected Assets & Attack Surface
- Backend configuration/authentication:
backend/webdav/webdav.go:127-139,170-206,440-530 - Shared redirect callback:
lib/rest/rest.go:218-231 - HTTP client:
fs/fshttp/http.go:311-329 - Credentials: Basic passwords, bearer authorization, SharePoint/session cookies, and configured secret headers
- Confirmed affected version:
<= v1.74.0-240
3. Technical Root Cause Analysis
PreserveMethodRedirectFn limits redirect count and restores the original method, but it does not reject a transport downgrade or compare the full origin tuple. The client therefore relies on Go's hostname-oriented sensitive-header forwarding rules. Those rules can preserve Authorization and Cookie on a same-host redirect even when the new scheme is plaintext HTTP.
4. Proof-of-Concept & Evidence
- Configure the actual WebDAV backend with Basic credentials and a Cookie.
- Have the TLS endpoint return
307 Temporary Redirectto an HTTP listener on the same hostname and a different port. - rclone follows the redirect while preserving the WebDAV method.
- The plaintext listener receives both the Basic
Authorizationvalue and Cookie.
5. Impact Assessment
An on-path observer can reuse the captured password, bearer token, or session cookie for the account's permitted WebDAV operations. Confidentiality, integrity, and availability impact depend on that account's permissions.
6. Remediation Guidance
- Reject every HTTPS-to-HTTP redirect before replay.
- Forward authenticated requests by default only when scheme, hostname, and effective port are unchanged.
- Strip authorization, cookies, proxy credentials, and configured secret headers on all other redirects.
- Put necessary provider exceptions behind exact destination allowlists.
- Cover
301,302,303,307, and308in regression tests.
Impact
GHSA-H4MF-4V27-HGGJ has a CVSS score of 5.3 (Medium). The vector is reachable from an adjacent network, 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 (1.75.0); 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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Frequently Asked Questions
- What is GHSA-H4MF-4V27-HGGJ? GHSA-H4MF-4V27-HGGJ is a medium-severity security vulnerability in github.com/rclone/rclone (go), affecting versions <= 1.74.0. It is fixed in 1.75.0.
- How severe is GHSA-H4MF-4V27-HGGJ? GHSA-H4MF-4V27-HGGJ has a CVSS score of 5.3 (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 github.com/rclone/rclone are affected by GHSA-H4MF-4V27-HGGJ? github.com/rclone/rclone (go) versions <= 1.74.0 is affected.
- Is there a fix for GHSA-H4MF-4V27-HGGJ? Yes. GHSA-H4MF-4V27-HGGJ is fixed in 1.75.0. Upgrade to this version or later.
- Is GHSA-H4MF-4V27-HGGJ exploitable, and should I be worried? Whether GHSA-H4MF-4V27-HGGJ 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 GHSA-H4MF-4V27-HGGJ 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 GHSA-H4MF-4V27-HGGJ? Upgrade
github.com/rclone/rcloneto 1.75.0 or later.