CVE-2025-6454: GitLab SSRF Vulnerability

CVE-2025-6454 Overview

CVE-2025-6454 is a Server-Side Request Forgery (SSRF) vulnerability [CWE-918] affecting GitLab Community Edition (CE) and Enterprise Edition (EE). The flaw exists in all versions from 16.11 before 18.1.6, 18.2 before 18.2.6, and 18.3 before 18.3.2. Authenticated users can inject crafted sequences to make unintended internal requests through proxy environments. GitLab released patched versions on September 10, 2025 to address the issue.

Critical Impact

Authenticated attackers can pivot through GitLab proxy environments to reach internal services, potentially compromising confidentiality, integrity, and availability of backend systems.

Affected Products

• GitLab Community Edition (CE) versions 16.11 through 18.1.5
• GitLab Enterprise Edition (EE) versions 18.2 through 18.2.5
• GitLab CE/EE versions 18.3 through 18.3.1

Discovery Timeline

• 2025-09-10 - GitLab releases patch versions 18.1.6, 18.2.6, and 18.3.2
• 2025-09-12 - CVE-2025-6454 published to NVD
• 2025-09-20 - Last updated in NVD database

Technical Details for CVE-2025-6454

Vulnerability Analysis

The vulnerability is classified as Server-Side Request Forgery under [CWE-918]. GitLab improperly handles user-controlled input that is passed through proxy environments. An authenticated user can inject crafted sequences that manipulate proxy request handling. The result is that GitLab makes HTTP requests to internal destinations that the user should not be able to reach directly.

SSRF flaws in collaboration platforms like GitLab are notable because they expose cloud metadata endpoints, internal APIs, and unauthenticated services behind perimeter controls. Exploitation requires only low privileges and no user interaction, making it accessible to any user with a valid GitLab account on an affected instance.

The attack delivers high impact to confidentiality, integrity, and availability. A successful SSRF can read internal-only data, trigger state-changing requests on internal services, or disrupt dependent backends.

Root Cause

The root cause is insufficient validation and sanitization of input that flows into proxy request construction. GitLab does not adequately filter crafted sequences that redirect requests away from intended external destinations. Refer to the GitLab Issue Tracker Entry for additional technical context.

Attack Vector

An authenticated attacker submits input containing crafted sequences to a GitLab feature that issues outbound requests through a proxy. GitLab processes the input and makes a request to an attacker-chosen internal endpoint. The attacker receives or influences the response, enabling reconnaissance and abuse of internal services. The full disclosure is documented in HackerOne Report #3162711.

Detection Methods for CVE-2025-6454

Indicators of Compromise

• Outbound HTTP requests from the GitLab application server to internal IP ranges (RFC1918, 169.254.169.254, or loopback) that do not match normal integration patterns.
• Proxy access logs showing requests with malformed hostnames, embedded credentials, or unusual URL encoding from GitLab workers.
• Unexpected hits on cloud instance metadata endpoints originating from the GitLab service account.
• Spikes in authenticated user activity correlated with anomalous outbound connection attempts from GitLab.

Detection Strategies

• Inspect GitLab production.log and workhorse.log for repeated external request features invoked with unusual URLs or hostnames.
• Correlate GitLab user audit events with egress proxy logs to identify users generating internal-bound traffic.
• Run version checks across GitLab instances to identify hosts still on vulnerable releases before 18.1.6, 18.2.6, or 18.3.2.

Monitoring Recommendations

• Forward GitLab application, Workhorse, and proxy logs to a centralized analytics platform for correlation.
• Alert on any GitLab-originated traffic to cloud metadata services or internal management interfaces.
• Baseline outbound destinations from GitLab and alert on deviations, particularly toward private address space.

How to Mitigate CVE-2025-6454

Immediate Actions Required

• Upgrade GitLab CE/EE to version 18.1.6, 18.2.6, or 18.3.2 depending on your current major branch.
• Audit recent authenticated user activity on the GitLab instance for unusual request patterns to internal hosts.
• Restrict outbound network access from the GitLab application tier using egress firewall rules.
• Rotate any secrets or tokens that may have been exposed by internal services reachable through GitLab.

Patch Information

GitLab released fixed versions 18.1.6, 18.2.6, and 18.3.2 on September 10, 2025. Administrators should apply the appropriate patch based on their deployed branch. Full details are available in the GitLab Patch Release Notes.

Workarounds

• Block GitLab application servers from initiating connections to internal subnets, cloud metadata endpoints (169.254.169.254), and loopback addresses at the network layer.
• Disable or restrict GitLab features that issue outbound requests on behalf of users, such as webhooks and repository imports, until patching is complete.
• Require IMDSv2 on AWS-hosted GitLab instances to mitigate metadata abuse.

# Example egress restriction using iptables on a GitLab application host
iptables -A OUTPUT -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -d 10.0.0.0/8 -p tcp -m multiport ! --dports 80,443 -j REJECT
iptables -A OUTPUT -d 192.168.0.0/16 -p tcp -m multiport ! --dports 80,443 -j REJECT
iptables -A OUTPUT -d 127.0.0.0/8 ! -o lo -j REJECT