CVE-2026-102828: simple-git unsafe-operation guard does not block trailer command configuration

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.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 30: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 30% of all scored CVEs (low). 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 simple-git (npm) >= 3.15.0, < 4.0.1, fixed in 4.0.1. Check your lockfile, including transitive dependencies.

What it is

simple-git, an interface for running git commands in any node.js application, enables applications to execute Git operations from JavaScript. From 3.15.0 until 4.0.1, the default blockUnsafeOperationsPlugin does not classify trailer. .cmd as unsafe configuration. An application that passes attacker-controlled values through SimpleGitOptions.config or inline -c arguments can therefore allow Git to invoke an attacker-selected shell command when git interpret-trailers processes the configured trailer. The command executes with the operating-system identity and permissions of the Node.js process. This issue is fixed in 4.0.1.

From the GitHub advisory

Affected product

The default blockUnsafeOperationsPlugin in simple-git when an application permits untrusted values to reach SimpleGitOptions.config or Git inline configuration arguments such as -c = .

Summary

trailer. .cmd is not recognized as unsafe by the default guard. Therefore, a configured inline value reaches Git without a GitPluginError.

Git documents trailer. .cmd as a shell command invoked by git interpret-trailers. An application that relies on the default plugin to reject unsafe configuration can therefore execute a command supplied through an untrusted trailer-command configuration value.

Weakness type: CWE-78, CWE-184.

Product: simple-git (npm) · Assigned by: GitHub_M · Published: 2026-09-29

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: high (needs special conditions)
• Attack requirements: present (depends on deployment conditions)
• Privileges required: none (no login)
• User interaction: none

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 none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.38% probability of exploitation activity in the next 30 days; percentile 30.

Timeline

• 2026-09-29 — CVE record published by GitHub_M
• 2026-09-30 — CVE record last updated
• 2026-10-05 — GitHub-reviewed advisory GHSA-x6jw-m9v5-85vh 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-x6jw-m9v5-85vh github.com
2. CVE.org record CVE-2026-102828 cve.org
3. NVD entry CVE-2026-102828 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

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