Summary
@zereight/mcp-gitlab has multiple safety-control bypasses: execute_graphql read-only + allow-list bypass, unauthenticated transports, session-exhaustion DoS
@zereight/mcp-gitlab exposes GitLab to an LLM agent while relying on read-only mode, a project allow-list, and transport auth as its safety controls. Five defects defeat those controls. Under the MCP threat model, tool-call arguments/content can be shaped by untrusted input (prompt injection) or a malicious client.
Reviewed commit: 60adcc0de5b0e96c4c2029f7a25d2775946421d8 (package version 2.1.28). Source review only; PoCs are local/offline.
- F1 (HIGH) execute_graphql defeats BOTH read-only mode and GITLAB_ALLOWED_PROJECT_IDS.
- F2 (HIGH, deployment-conditional) Streamable HTTP /mcp unauthenticated under cookie-jar / device-flow credentials.
- F3 (MEDIUM) SSE unauthenticated by default, no Origin/Host validation (DNS rebinding).
- F4 (HIGH) unauthenticated session/transport-exhaustion DoS (token check is syntactic only).
- F5 (LOW) CI job trace returned verbatim (prompt-injection surface).
Details
F1, index.ts:9194-9245 (case "execute_graphql"), guard at :9196, detector in utils/graphql-query.ts.
(a) Read-only bypass: graphqlQueryContainsWriteOperation() strips comments/strings then tests /(?:^|[};]\s*)(mutation|subscription)\b/. GraphQL treats commas as insignificant, and stripGraphQLCommentsAndStrings does not remove them, so a document beginning with ,mutation{...} executes as a write but is classified read-only. (b) Allow-list bypass: the handler never calls getEffectiveProjectId() or rejectIfProjectScopedDeployment() (unlike other tools), so a raw GraphQL body reaches /api/graphql with the server token against any project the token can access, regardless of GITLAB_ALLOWED_PROJECT_IDS. execute_graphql is listed in readOnlyTools (tools/registry.ts:1288).
F2, index.ts:1048-1052 forces REMOTE_AUTHORIZATION/GITLAB_MCP_OAUTH only when started with a PAT or job token; hasCookie (:1029) and useOAuth (:1026) are absent from the gate. Started with --cookie-path or --use-oauth, validation passes and mcpBearerAuth degrades to next() (:12903). Every /mcp caller is unauthenticated while buildAuthHeaders() attaches the server's live session upstream.
F3, index.ts:12276 requireSseAuth is a pass-through when SSE_AUTH_TOKEN is unset (default), and the SSE transport (:12290) is created with no enableDnsRebindingProtection/allowedHosts/allowedOrigins. On the default loopback bind, a malicious web page can DNS-rebind to drive the local server with the operator's GitLab credentials.
F4, index.ts:12387 validateToken only checks length>=20 and charset (no upstream verification); parseAuthHeaders returns AuthData for any such string; new sessions are admitted purely on capacity (:12938, MAX_SESSIONS default 1000), and the per-session rate limiter only runs when a sessionId already exists. So garbage-token initialize floods fill all session slots for SESSION_TIMEOUT_SECONDS (default 3600s) -> 503 for legitimate users.
F5, index.ts:10898-10911 (get_pipeline_job_output) returns the CI job trace to the model verbatim. Job logs are attacker-influenceable (e.g. a fork MR pipeline), so embedded instructions become model context and, combined with F1, can escalate to writes.
PoC (local, deterministic)
F1 detector (replicates the shipped logic, no network):
isWrite("mutation{deleteProject(input:{id:1}){errors}}") -> DETECTED
isWrite(",mutation{deleteProject(input:{id:1}){errors}}") -> BYPASS (executes as a write under read-only mode)
F2 (local GitLab + cookie file):
STREAMABLE_HTTP=true GITLAB_AUTH_COOKIE_PATH=./cookies.txt GITLAB_API_URL=http://localhost:8080/api/v4 node build/index.js
# starts without an auth error; from another shell with NO credentials:
curl -s http://127.0.0.1:3002/mcp -H 'Content-Type: application/json' -H 'Accept: application/json, text/event-stream'
-d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"poc","version":"0"}}}'
F4 (REMOTE_AUTHORIZATION mode):
for i in $(seq 1 1000); do curl -s -o /dev/null http://127.0.0.1:3002/mcp
-H 'Content-Type: application/json' -H 'Accept: application/json, text/event-stream'
-H 'Private-Token: aaaaaaaaaaaaaaaaaaaaaaaa'
-d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"x","version":"0"}}}'; done
# subsequent legitimate initialize -> 503 "Maximum 1000 concurrent sessions allowed"
Impact
A semi-trusted client or a prompt-injected agent can perform arbitrary GitLab writes while the operator believes the server is read-only, against projects outside the allow-list, up to the token's privileges (F1). Anyone able to reach the port (directly or via DNS rebinding on loopback) can use the server's GitLab credentials with no authentication (F2/F3). An unauthenticated attacker can deny service with ~1000 trivial requests (F4). Attacker-influenced CI logs can steer the agent (F5).
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
GHSA-5648-RGJ9-V224 has a CVSS score of 8.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.1.30); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
Parse execute_graphql with a real GraphQL parser and reject non-query operations; enforce project scope or disable the tool under an allow-list (F1). Extend the startup gate to (hasToken || hasJobToken || hasCookie || useOAuth) and ship a mandatory Streamable-HTTP auth token (F2). Enable SDK DNS-rebinding protection with allowedHosts/allowedOrigins and require SSE_AUTH_TOKEN by default (F3). Validate tokens upstream before allocating a session, rate-limit new-session creation per IP, lower idle timeout (F4). Frame externally-sourced content as untrusted and cap size (F5).
Frequently Asked Questions
- What is GHSA-5648-RGJ9-V224? GHSA-5648-RGJ9-V224 is a high-severity incorrect authorization vulnerability in @zereight/mcp-gitlab (npm), affecting versions < 2.1.30. It is fixed in 2.1.30. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
- How severe is GHSA-5648-RGJ9-V224? GHSA-5648-RGJ9-V224 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of @zereight/mcp-gitlab are affected by GHSA-5648-RGJ9-V224? @zereight/mcp-gitlab (npm) versions < 2.1.30 is affected.
- Is there a fix for GHSA-5648-RGJ9-V224? Yes. GHSA-5648-RGJ9-V224 is fixed in 2.1.30. Upgrade to this version or later.
- Is GHSA-5648-RGJ9-V224 exploitable, and should I be worried? Whether GHSA-5648-RGJ9-V224 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-5648-RGJ9-V224 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-5648-RGJ9-V224? Upgrade
@zereight/mcp-gitlabto 2.1.30 or later.