Comprehensive Technical Analysis of CVE-2026-20750

CVE ID: CVE-2026-20750 CVSS Score: 9.1 (Critical) Affected Software: Gitea (versions prior to 1.25.4) Vulnerability Type: Improper Access Control (Authorization Bypass)

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1. Vulnerability Assessment & Severity Evaluation

Vulnerability Overview

CVE-2026-20750 is a critical authorization bypass vulnerability in Gitea, a self-hosted Git service. The flaw stems from improper validation of project ownership in organization-level project operations, allowing an attacker with write access to one organization’s project to modify projects in a different organization where they should not have permissions.

CVSS Vector & Severity Breakdown

The CVSS v3.1 score of 9.1 (Critical) is justified by the following metrics:

Metric	Value	Explanation
Attack Vector (AV)	Network	Exploitable remotely via HTTP(S) requests.
Attack Complexity (AC)	Low	No special conditions required; straightforward exploitation.
Privileges Required (PR)	Low	Attacker only needs write access to a single project (not admin).
User Interaction (UI)	None	No user interaction required.
Scope (S)	Changed	Impact extends beyond the vulnerable component (affects other organizations).
Confidentiality (C)	High	Unauthorized modification of projects may expose sensitive data.
Integrity (I)	High	Attacker can alter project configurations, code, or metadata.
Availability (A)	High	Potential for denial-of-service via project corruption.

Risk Assessment

• Exploitability: High (low skill required, no authentication bypass needed).
• Impact: Severe (unauthorized cross-organization project modifications).
• Likelihood of Exploitation: High (especially in multi-tenant Gitea instances).
• Business Impact: Critical for organizations relying on Gitea for source code management (SCM), CI/CD pipelines, or DevOps workflows, as it could lead to code tampering, supply chain attacks, or data exfiltration.

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2. Potential Attack Vectors & Exploitation Methods

Attack Prerequisites

• Valid user account with write access to at least one project in any organization.
• Network access to the Gitea instance (HTTP/HTTPS).

Exploitation Steps

1. Identify Target Organizations & Projects

   • The attacker enumerates organizations and projects they do not have explicit access to (e.g., via API calls or UI inspection).
   • Example: If the attacker has write access to OrgA/Project1, they may attempt to modify OrgB/Project2.

2. Craft Malicious Request

   • The vulnerability likely resides in project modification API endpoints (e.g., /api/v1/repos/{org}/{repo} or /api/v1/org/{org}/projects).
   • The attacker sends a forged request with manipulated parameters (e.g., org or project_id) to bypass ownership checks.

3. Execute Unauthorized Actions

   • Modify project settings (e.g., visibility, collaborators).
   • Alter repository contents (e.g., push malicious code, modify .gitea/workflows for CI/CD hijacking).
   • Delete or corrupt projects (denial-of-service).
   • Exfiltrate sensitive data (e.g., via modified webhooks or CI/CD pipelines).

Proof-of-Concept (PoC) Scenario

A hypothetical exploit might involve:

POST /api/v1/repos/OrgB/TargetRepo HTTP/1.1
Host: gitea.example.com
Authorization: token <ATTACKER_TOKEN>
Content-Type: application/json

{
  "name": "TargetRepo",
  "description": "Malicious modification via CVE-2026-20750",
  "private": false  # Changing visibility to public
}

If the vulnerability exists, this request would succeed despite the attacker not being a member of OrgB.

Post-Exploitation Impact

• Supply Chain Attacks: Inject malicious code into repositories used by other teams.
• Privilege Escalation: Modify project collaborators to gain higher privileges.
• Data Exfiltration: Leak sensitive data via modified webhooks or CI/CD pipelines.
• Denial-of-Service: Delete or corrupt critical projects.

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3. Affected Systems & Software Versions

Vulnerable Versions

• All Gitea versions prior to 1.25.4 are affected.
• Gitea 1.25.4 contains the patch (released in the referenced advisory).

Deployment Scenarios at Risk

• Self-hosted Gitea instances (most critical, as they may lack auto-updates).
• Cloud-hosted Gitea services (if not patched by the provider).
• CI/CD integrations (e.g., Gitea Actions, Drone, Jenkins) where project modifications could lead to pipeline hijacking.

Unaffected Systems

• Gitea 1.25.4 and later (patched).
• Other Git platforms (GitHub, GitLab, Bitbucket) are not affected.

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4. Recommended Mitigation Strategies

Immediate Actions

1. Upgrade to Gitea 1.25.4 or Later

   • Primary fix: Apply the patch from Gitea’s security advisory.
   • Verification: Confirm the fix by testing project modification requests across organizations.

2. Temporary Workarounds (If Upgrade is Delayed)

   • Restrict API Access: Limit API access to trusted IPs via firewall rules or reverse proxy (e.g., Nginx, Cloudflare).
   • Disable Project Modification APIs: If possible, disable non-essential project modification endpoints.
   • Monitor for Suspicious Activity:
     • Log and alert on cross-organization project modifications.
     • Use Gitea’s audit logging (if enabled) to detect unauthorized changes.

3. Incident Response Preparedness

   • Isolate Affected Instances: If exploitation is suspected, take the Gitea instance offline for forensic analysis.
   • Rotate Credentials: Invalidate all API tokens and session cookies if a breach is confirmed.
   • Review Project Changes: Audit all recent project modifications for unauthorized activity.

Long-Term Security Recommendations

• Implement Least Privilege: Restrict project write access to only necessary users.
• Enable Multi-Factor Authentication (MFA): Reduce the risk of credential compromise.
• Regular Vulnerability Scanning: Use tools like Trivy, Nessus, or OpenVAS to detect unpatched Gitea instances.
• Network Segmentation: Isolate Gitea instances from other critical systems.
• Automated Patch Management: Use tools like Ansible, Puppet, or Kubernetes operators to ensure timely updates.

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5. Impact on the Cybersecurity Landscape

Broader Implications

• Supply Chain Risks: Gitea is widely used in DevOps and CI/CD pipelines, making this vulnerability a high-value target for supply chain attacks.
• Multi-Tenant Environments: Organizations using Gitea for multiple teams or customers are at heightened risk of cross-tenant attacks.
• Open-Source Security: Highlights the need for rigorous access control testing in open-source SCM tools.

Comparison to Similar Vulnerabilities

Vulnerability	CVE	CVSS	Impact	Key Difference
Gitea Auth Bypass	CVE-2026-20750	9.1	Cross-org project modification	Exploits project ownership validation
GitLab CI Lint RCE	CVE-2021-22205	10.0	Remote code execution	Requires CI/CD pipeline access
GitHub Actions RCE	CVE-2020-15228	9.8	Workflow hijacking	Exploits GitHub Actions misconfigurations

Threat Actor Interest

• APT Groups: May exploit this for espionage or supply chain attacks.
• Cybercriminals: Could use it for cryptojacking, ransomware deployment, or data theft.
• Bug Bounty Hunters: High-value target for zero-day research.

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6. Technical Details for Security Professionals

Root Cause Analysis

The vulnerability stems from insufficient authorization checks in Gitea’s project management logic. Specifically:

• When a user submits a request to modify a project (e.g., via /api/v1/repos/{org}/{repo}), Gitea fails to verify whether the user has explicit permissions for the target organization.
• Instead, it only checks if the user has write access to any project (regardless of organization), leading to cross-organization privilege escalation.

Patch Analysis

The fix (introduced in PR #36318 and PR #36373) involves:

1. Enforcing Organization-Level Checks:
   • Before processing project modifications, Gitea now explicitly verifies that the user is a member of the target organization.
2. Input Validation:
   • Stricter validation of org and project_id parameters to prevent parameter tampering.
3. Audit Logging Enhancements:
   • Improved logging of cross-organization project modifications for forensic analysis.

Exploitation Detection

Security teams can detect exploitation attempts via:

• Web Application Firewall (WAF) Rules:
  • Block requests with mismatched org and project_id parameters.
  • Alert on unusual API call patterns (e.g., rapid cross-organization modifications).
• SIEM Correlation:
  • Monitor for project modifications by users who are not members of the target organization.
  • Example Splunk query:

    index=gitea_logs sourcetype=gitea_api
    | search action="repo.update" AND user NOT IN (SELECT user FROM org_members WHERE org="{target_org}")
    

• File Integrity Monitoring (FIM):
  • Detect unauthorized changes to .gitea/workflows or README.md files.

Forensic Investigation Steps

If exploitation is suspected:

1. Collect Logs:
   • Gitea API logs (/var/log/gitea/*.log).
   • Web server logs (Nginx/Apache).
   • Database logs (if using MySQL/PostgreSQL).
2. Analyze Project Changes:
   • Compare git history (git log) for unauthorized commits.
   • Review project settings for unexpected modifications.
3. Check for Persistence:
   • Inspect webhooks, CI/CD pipelines, and cron jobs for malicious modifications.
4. Memory Forensics (if applicable):
   • Use Volatility or Rekall to analyze running Gitea processes for in-memory exploits.

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Conclusion

CVE-2026-20750 represents a critical authorization bypass in Gitea, enabling cross-organization project manipulation with severe implications for supply chain security, data integrity, and availability. Organizations using Gitea must immediately upgrade to version 1.25.4 and implement compensating controls (e.g., WAF rules, SIEM monitoring) to mitigate risk.

Given the high exploitability and impact, this vulnerability is likely to be actively targeted by threat actors. Security teams should prioritize patching, monitoring, and incident response preparedness to prevent exploitation.

Further Reading

• Gitea Security Advisory (GHSA-h4fh-pc4w-8w27)
• Gitea 1.25.4 Release Notes
• OWASP Access Control Cheat Sheet