GHSA-h4mf-4v27-hggj is a medium-severity (CVSS 5.3) CWE-319 vulnerability in github.com/rclone/rclone. A fix is available for github.com/rclone/rclone — see the affected versions and patch details below.
rclone: WebDAV Credentials Survive a Same-Host HTTPS-to-HTTP Redirect
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-h4mf-4v27-hggj.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-h4mf-4v27-hggj plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/rclone/rcloneReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/rclone/rclone | all versions | 1.75.0go get github.com/rclone/rclone@v1.75.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/rclone/rclone, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/rclone/rclone to 1.75.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h4mf-4v27-hggj is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-h4mf-4v27-hggj can be triaged on real exposure rather than presence alone.
Tailored to GHSA-h4mf-4v27-hggj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-h4mf-4v27-hggj in your dependencies?
O3 Security finds GHSA-h4mf-4v27-hggj across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.