GHSA-964w-f6gj-5236 is a medium-severity (CVSS 5.3) CWE-41 vulnerability in github.com/patrickhener/goshs/v2. O3 Security confirms whether GHSA-964w-f6gj-5236 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
goshs has ACL Bypass & Path Traversal
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-964w-f6gj-5236.
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-964w-f6gj-5236 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 371,625 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/patrickhener/goshs/v2🐹goshs.de/goshs/v2🐹github.com/patrickhener/goshs🐹goshs.de/goshsReal-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
Summary
sendFile derives the served filename from the raw request path while opening the file from the cleaned path, so appending a trailing slash empties the derived name and defeats both the never-serve rule for the ACL file and the block list.
Finding (Medium): trailing-slash ACL and hidden-file bypass
httpserver/handler.go, sendFile (lines 789-801) takes the filename from the RAW req.URL.Path while the file itself is opened from the filepath.Clean-ed path. The two disagree, and a trailing slash makes the derived name the empty string. Both protections key on that derived name, so both are defeated: the rule that never serves the .goshs ACL file, and the acl.Block list.
Measured, with negative controls:
GET /blocked/secret.txt -> 404 (control, correctly blocked)
GET /blocked/secret.txt/ -> 200 + contents
GET /blocked/.goshs/ -> 200, returns the ACL file itself,
including the admin:$2a$... bcrypt hash
Unauthenticated when the ACL is configured block-only (common usage). Stated precisely: AUTHENTICATION IS NOT BYPASSED. An unauthenticated request against a directory protected by authentication still returns 401 under the same trick; I tested that. The claim is specifically that the block list and the ACL-file protection are bypassed. In-tree evidence that sendFile is the defect: the sibling handlers doDir and bulkDownload both derive the name correctly; sendFile is the lone outlier.
Suggested fixes
- Derive the served filename from the same cleaned path used to open the file, so the authorization decision and the file access cannot disagree.
Tooling
AI assistance was used while investigating. The finding was reproduced against a running server on loopback with negative controls, including the 404-versus-200 pair and the authenticated-directory control that shows authentication is not affected.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/patrickhener/goshs/v2 | all versions | 2.1.5-0.20260727065949-f3ef599e4091 |
| 🐹Go | goshs.de/goshs/v2 | all versions | 2.1.5-0.20260727065949-f3ef599e4091 |
| 🐹Go | github.com/patrickhener/goshs | all versions | No fix |
| 🐹Go | goshs.de/goshs | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/patrickhener/goshs/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/patrickhener/goshs/v2 to 2.1.5-0.20260727065949-f3ef599e4091 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-964w-f6gj-5236 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 pinpoints whether GHSA-964w-f6gj-5236 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-964w-f6gj-5236. 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-964w-f6gj-5236 in your dependencies?
O3 detects GHSA-964w-f6gj-5236 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.