CVE-2025-52477 Overview
CVE-2025-52477 is a Server-Side Request Forgery (SSRF) vulnerability affecting Octo-STS, a GitHub App that functions as a Security Token Service (STS) for the GitHub API. Versions prior to v0.5.3 are vulnerable to unauthenticated SSRF attacks through exploitation of fields in OpenID Connect (OIDC) tokens. Attackers can craft malicious tokens that trigger internal network requests, potentially exposing sensitive information through reflected error logs.
Critical Impact
Unauthenticated attackers can abuse OIDC token fields to force internal network requests, potentially leaking sensitive information from error logs and enabling reconnaissance of internal infrastructure.
Affected Products
- Octo-STS versions prior to v0.5.3
- GitHub App deployments using vulnerable Octo-STS instances
- Organizations relying on Octo-STS for GitHub API token management
Discovery Timeline
- 2025-06-26 - CVE-2025-52477 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-52477
Vulnerability Analysis
This vulnerability is classified as CWE-918 (Server-Side Request Forgery). The flaw exists in how Octo-STS processes fields within OpenID Connect tokens without proper input validation. When a malicious OIDC token is submitted to the application, the unvalidated fields can be manipulated to cause the server to make arbitrary HTTP requests to internal or external endpoints.
The SSRF vulnerability is particularly concerning because it is unauthenticated, meaning attackers do not need valid credentials to exploit it. The attack can be leveraged for internal network reconnaissance, accessing internal services, and extracting sensitive information through error message reflection in logs.
Root Cause
The root cause stems from insufficient input sanitization of OpenID Connect token fields before they are processed by the application. When Octo-STS receives an OIDC token, certain fields within the token are used to construct internal requests without proper validation or URL scheme restrictions. This allows attackers to inject malicious URLs or hostnames that redirect server-side requests to unintended destinations.
Additionally, the application's logging mechanism was not properly redacting sensitive information, causing error responses from SSRF attempts to be reflected in logs where they could potentially be accessed by attackers.
Attack Vector
The attack is network-based and requires no authentication or user interaction. An attacker crafts a malicious OpenID Connect token with specially crafted field values containing internal network addresses or sensitive endpoints. When this token is submitted to Octo-STS for processing, the application uses these field values to make server-side HTTP requests.
The vulnerability allows attackers to probe internal network infrastructure, access internal services that should not be externally accessible, and potentially extract sensitive configuration or metadata from internal endpoints. Error messages from failed requests may also reveal information about the internal network topology or application configuration.
Detection Methods for CVE-2025-52477
Indicators of Compromise
- Unusual outbound HTTP requests from Octo-STS servers to internal IP ranges (e.g., 10.x.x.x, 172.16.x.x, 192.168.x.x)
- OIDC token submissions containing non-standard or suspicious URL values in token fields
- Error logs containing references to internal hostnames, metadata endpoints, or cloud provider instance metadata URLs
- Anomalous network traffic patterns from the Octo-STS application to localhost or link-local addresses
Detection Strategies
- Monitor Octo-STS application logs for OIDC token parsing errors that reference internal URLs or IP addresses
- Implement network-level monitoring to detect outbound connections from Octo-STS to internal network segments
- Deploy Web Application Firewall (WAF) rules to detect SSRF payloads in token-related request parameters
- Set up alerts for requests to cloud metadata endpoints (e.g., 169.254.169.254) originating from the Octo-STS service
Monitoring Recommendations
- Enable verbose logging on Octo-STS and centralize logs for security analysis
- Implement egress filtering to restrict outbound network access from the Octo-STS application
- Monitor for version information to ensure deployments are running v0.5.3 or later
- Conduct periodic security assessments of OIDC token processing workflows
How to Mitigate CVE-2025-52477
Immediate Actions Required
- Upgrade Octo-STS to version v0.5.3 or later immediately
- Review application logs for evidence of exploitation attempts prior to patching
- Implement network segmentation to limit potential SSRF impact
- Block outbound traffic from Octo-STS to internal network ranges and cloud metadata endpoints where possible
Patch Information
The vulnerability has been resolved in Octo-STS version v0.5.3. This release includes patch sets that sanitize input from OIDC token fields and redact sensitive information from logging output. Two commits address this vulnerability:
- Commit 0f177fd - Input sanitization improvements
- Commit b3976e3 - Logging redaction enhancements
For detailed information, refer to the GitHub Security Advisory GHSA-h3qp-hwvr-9xcq.
Workarounds
- Implement network-level controls to restrict outbound connections from the Octo-STS service to only necessary external endpoints
- Deploy a reverse proxy or WAF in front of Octo-STS to filter and validate incoming OIDC tokens before they reach the application
- Restrict access to the Octo-STS service to trusted networks or authenticated sources until patching is complete
- Disable or filter logging output to prevent potential information leakage through error messages
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
