Summary
goshs has ACL Bypass & Path Traversal
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.
Impact
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-66064 has a CVSS score of 5.3 (Medium). 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 (2.1.5-0.20260727065949-f3ef599e4091); 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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github.com/patrickhener/goshs/v2 to 2.1.5-0.20260727065949-f3ef599e4091 or later; goshs.de/goshs/v2 to 2.1.5-0.20260727065949-f3ef599e4091 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-66064? CVE-2026-66064 is a medium-severity path traversal vulnerability in github.com/patrickhener/goshs/v2 (go), affecting versions <= 2.1.4. It is fixed in 2.1.5-0.20260727065949-f3ef599e4091. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-66064? CVE-2026-66064 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 packages are affected by CVE-2026-66064?
github.com/patrickhener/goshs/v2(go) (versions <= 2.1.4)goshs.de/goshs/v2(go) (versions <= 2.1.4)github.com/patrickhener/goshs(go) (versions <= 1.1.4)goshs.de/goshs(go) (versions <= 1.1.4)
- Is there a fix for CVE-2026-66064? Yes. CVE-2026-66064 is fixed in 2.1.5-0.20260727065949-f3ef599e4091. Upgrade to this version or later.
- Is CVE-2026-66064 exploitable, and should I be worried? Whether CVE-2026-66064 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-2026-66064 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-2026-66064?
- Upgrade
github.com/patrickhener/goshs/v2to 2.1.5-0.20260727065949-f3ef599e4091 or later - Upgrade
goshs.de/goshs/v2to 2.1.5-0.20260727065949-f3ef599e4091 or later
- Upgrade