How severe is CVE-2026-55887?

No CVSS score has been assigned to CVE-2026-55887 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-55887?

CVE-2026-55887 affects the following packages: github.com/docker/mcp-gateway (Go). Ecosystems affected: Go.

How do I fix CVE-2026-55887?

Update github.com/docker/mcp-gateway to 0.42.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55887 is resolved across your whole dependency graph.

How do I detect CVE-2026-55887 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/docker/mcp-gateway, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-55887 if there is no patch (or I can't update yet)?

Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.

Is CVE-2026-55887 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55887 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-55887?

CVE-2026-55887 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 12th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-55887?

CVE-2026-55887 is classified as CWE-88 (CWE-88). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-55887 published, and has it been updated?

CVE-2026-55887 was published on September 15, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-55887 — mcp-gateway

Fix: docker/mcp-gateway@306d2d9

CVE-2026-55887 is a CWE-88 vulnerability in github.com/docker/mcp-gateway. A fix is available for github.com/docker/mcp-gateway — see the affected versions and patch details below.

MCP Gateway: Argument injection via OCI image label YAML in Docker MCP Gateway

Also known asGHSA-r2xf-7jw5-pjg6GO-2026-5604

Published

Sep 15, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55887.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs12th percentile — riskier than 12% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/docker/mcp-gateway

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A maliciously crafted OCI image label can inject arbitrary arguments into the docker run command line constructed by the MCP Gateway. An attacker who controls an image that the victim references via docker://, or that the victim's catalog pulls a snapshot from, can mount the host filesystem, run as UID 0, and execute arbitrary code on the host.

Details

The io.docker.server.metadata OCI image label is YAML-unmarshalled directly into the wide catalog.Server struct, which carries runtime-shaping fields (Volumes, User, Command, ExtraHosts, AllowHosts, DisableNetwork, Env, Remote, SSEEndpoint, OAuth,Secrets, LongLived, Policy) alongside descriptive fields. Every runtime field carries a YAML tag, so the unmarshal mass-assigns from the attacker-controlled label content; only Image is overwritten afterwards. The gateway's container-launch code then appends those fields verbatim as docker run flags (-v, -u, --add-host) with no allowlist or origin check, and execs docker with the resulting argv.

Impact

A malicious image author can achieve arbitrary code execution as UID 0 on the host of a victim running an affected version of MCP Gateway. Attacker-injected -v /:/host, -u root, and -v /var/run/docker.sock:/var/run/docker.sock arguments reach the docker run invocation that launches the MCP server container, giving the attacker full host filesystem access and root execution. The container/host trust boundary is bypassed at container-creation time, so the --security-opt no-new-privileges flag the gateway applies provides no protection: no in-container privilege escalation is needed.

Patches

The OCI image-label parser now only populates descriptive fields from the image label, which excludes fields that control the container runtime.

Credit

This issue was reported by Jabr Al-Otaibi @ DarkCov working with TrendAI Zero Day Initiative

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/docker/mcp-gateway`	≥ 0.21.0&&< 0.42.2	0.42.2`go get github.com/docker/mcp-gateway@v0.42.2`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/docker/mcp-gateway, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/docker/mcp-gateway to 0.42.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55887 is resolved across your whole dependency graph.
Workarounds
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.

Frequently Asked Questions

## Summary A maliciously crafted OCI image label can inject arbitrary arguments into the `docker run` command line constructed by the MCP Gateway. An attacker who controls an image that the victim references via `docker://`, or that the victim's catalog pulls a snapshot from, can mount the host filesystem, run as UID 0, and execute arbitrary code on the host. ## Details The `io.docker.server.metadata` OCI image label is YAML-unmarshalled directly into the wide `catalog.Server` struct, which carries runtime-shaping fields (`Volumes`, `User`, `Command`, `ExtraHosts`, `AllowHosts`, `Disable

O3 Security · Impact-Aware SCA

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