CVE-2026-61560: @zereight/mcp-gitlab: Unauthenticated arbitrary file read via `upload_markdown` enables PAT exfiltration and full account takeover

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 2.9%, percentile 87: FIRST’s model estimates a 2.9% chance of exploitation activity in the next 30 days, higher than 87% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes @zereight/mcp-gitlab (npm) < 2.1.27, fixed in 2.1.27. Check your lockfile, including transitive dependencies.

What it is

@zereight/mcp-gitlab is a Model Context Protocol server for GitLab. Prior to version 2.1.27, the SSE transport mode (SSE=true) exposes all MCP tools without any authentication. The uploadmarkdown tool reads arbitrary files from the server's local filesystem via an unsanitized filepath parameter and uploads them to a GitLab project. Combined, any unauthenticated network-reachable attacker can read /proc/self/environ to steal the server's GITLABPERSONALACCESSTOKEN and achieve full GitLab account takeover. This is the default configuration for Docker deployments. Version 2.1.27 contains a patch.

From the GitHub advisory

Summary

The SSE transport mode (SSE=true) exposes all MCP tools without any authentication. The uploadmarkdown tool reads arbitrary files from the server's local filesystem via an unsanitized filepath parameter and uploads them to a GitLab project. Combined, any unauthenticated network-reachable attacker can read /proc/self/environ to steal the server's GITLABPERSONALACCESSTOKEN and achieve full GitLab account takeover. This is the default configuration for Docker deployments.

Details

Two issues chain together:

1. No authentication on SSE transport (src/index.ts:7350-7388)

Weakness type: CWE-22.

Product: @zereight/mcp-gitlab (npm) · Assigned by: GitHub_M · Published: 2026-09-15

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 2.90% probability of exploitation activity in the next 30 days; percentile 87.

Timeline

• 2026-09-15 — CVE record published by GitHub_M
• 2026-09-16 — CVE record last updated
• 2026-09-16 — GitHub-reviewed advisory GHSA-cv3r-c5h8-f4g5 published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-cv3r-c5h8-f4g5 github.com
2. CVE.org record CVE-2026-61560 cve.org
3. NVD entry CVE-2026-61560 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. github.com github.com
6. github.com github.com

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