← back to articles
view analysis
SECURITY ADVISORY / 01

CVE-2026-27771 Exploit & Vulnerability Analysis

Complete CVE-2026-27771 security advisory with proof of concept (PoC), exploit details, and patch analysis for gitea.

gitea products NVD ↗
Exploit PoC Vulnerability Patch Analysis

The Exploit

A low-privilege user able to call the composer package metadata API can retrieve metadata for a private package owner.

curl -i -H "Authorization: token ATTACKER_TOKEN" \
  "https://TARGET/api/packages/victimuser/composer"

The attacker receives 200 OK and JSON containing composer package metadata from victimuser, including source/distribution metadata that should have been restricted. On patched Gitea, the same request is rejected or filtered because the composer response helper now receives the request context and enforces permissions.

What the Patch Did

Before:

resp := createPackageMetadataResponse(setting.AppURL+"api/packages/"+ctx.Package.Owner.Name+"/composer", pds)

After:

resp := createPackageMetadataResponse(ctx, setting.AppURL+"api/packages/"+ctx.Package.Owner.Name+"/composer", pds)

The fix passes the HTTP request context into createPackageMetadataResponse, giving the metadata builder access to authentication/authorization state. This is a context propagation fix: the helper can now decide whether the caller is allowed to see private package source metadata.

Root Cause

This was an information disclosure bug (CWE-200): the composer package metadata endpoint built a response without supplying the request context to the helper that serializes package metadata. The attacker-controlled request arrives at /api/packages/<owner>/composer; the route constructs a response URL from ctx.Package.Owner.Name and calls createPackageMetadataResponse(...) without ctx. That helper therefore lacked the trust boundary information needed to decide if the caller was authorized for private package metadata, so it exposed sensitive source metadata regardless of visibility.

Why It Works

The only load-bearing change is the added ctx argument. Without that line, the helper still cannot inspect the caller’s auth state or package visibility and remains blind to whether private package metadata should be filtered. The rest of the patch is just signature propagation; the developer added the extra parameter so downstream code could perform permission-aware response generation. If that line were removed, the bug would still be exploitable.

Hardening Checklist

  • Pass request context into all helper functions that generate authorization-sensitive API responses.
  • Enforce package visibility checks before serializing metadata, using explicit authorization logic rather than implicit path-based assumptions.
  • Treat package metadata endpoints as sensitive resources and return http.StatusForbidden for unauthorized access.
  • Avoid constructing API responses from owner/package path values alone; include the caller’s ctx or auth token state in permission decisions.

References

  • https://nvd.nist.gov/vuln/detail/CVE-2026-27771

Frequently asked questions about CVE-2026-27771

What is CVE-2026-27771?

CVE-2026-27771 is a security vulnerability identified in gitea. This security advisory provides detailed technical analysis of the vulnerability, exploit methodology, affected versions, and complete remediation guidance.

Is there a PoC (proof of concept) for CVE-2026-27771?

Yes. This writeup includes proof-of-concept details and a technical exploit breakdown for CVE-2026-27771. Review the analysis sections above for the PoC walkthrough and code examples.

How does CVE-2026-27771 get exploited?

The technical analysis section explains the vulnerability mechanics, attack vectors, and exploitation methodology affecting gitea. PatchLeaks publishes this information for defensive and educational purposes.

What products and versions are affected by CVE-2026-27771?

CVE-2026-27771 affects gitea. Check the affected-versions section of this advisory for specific version ranges, vulnerable configurations, and compatibility information.

How do I fix or patch CVE-2026-27771?

The patch analysis section provides guidance on updating to patched versions, applying workarounds, and implementing compensating controls for gitea.

What is the CVSS score for CVE-2026-27771?

The severity rating and CVSS scoring for CVE-2026-27771 affecting gitea is documented in the vulnerability details section. Refer to the NVD entry for the current authoritative score.