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CVE-2026-102828 — simple-git

Fix: steveukx/git-js@d762810

CVE-2026-102828 is a OS Command Injection vulnerability in simple-git. A fix is available for simple-git — see the affected versions and patch details below.

simple-git unsafe-operation guard does not block trailer command configuration

Also known asGHSA-x6jw-m9v5-85vh
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 7, 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-2026-102828.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs18th percentile — riskier than 18% of all scored CVEsHighest risk
0.00%0.26%0.52%0.78%0.3%0.3%Oct 26Oct 26

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

Real-World Exposure

1 pkg affected
📦simple-git

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

Description

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 <key>=<value>.

Summary

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

Git documents trailer.<token>.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.

Technical details

simple-git/src/lib/git-factory.ts installs commandConfigPrefixingPlugin before blockUnsafeOperationsPlugin. The prefixing plugin in simple-git/src/lib/plugins/command-config-prefixing-plugin.ts turns every SimpleGitOptions.config entry into -c <key>=<value> before the unsafe-operation plugin evaluates the final argv.

In [email protected], blockUnsafeOperationsPlugin delegates to @simple-git/argv-parser. packages/argv-parser/src/vulnerabilities/detect-vulnerable-config-writes.ts compares parsed configuration writes against preventUnsafeConfig. That list has no matcher for trailer.<token>.cmd, so the invocation is allowed.

Git v2.39.5's Documentation/git-interpret-trailers.txt states that trailer.<token>.cmd specifies a shell command called to generate or modify a trailer.

Preconditions

The application must use an affected simple-git version with the default unsafe-operation plugin active and must pass attacker-controlled data into instance configuration or Git command arguments that configure trailer.<token>.cmd.

The invoked Git binary must support the documented trailer-command behavior, and the application must execute git interpret-trailers with the attacker-controlled configuration in scope. The command runs with the operating-system identity and permissions of the Node.js process.

Verification

Use an isolated test environment and a harmless executable test helper that records only its invocation.

Control: Configure core.editor=<test-helper> through SimpleGitOptions.config and invoke a benign Git task. The default plugin should throw GitPluginError before spawning Git because core.editor is present in preventUnsafeConfig.

Bypass: Configure trailer.audit.cmd=<test-helper> through the same option and invoke Git with the equivalent argv shape:

git -c trailer.audit.cmd=<test-helper> interpret-trailers --trailer audit:<value> <input-file>

A vulnerable build does not raise GitPluginError; Git invokes the test helper while processing the trailer. Confirm the helper invocation, then remove test artifacts.

Impact

An attacker who controls the stated configuration input can cause Git to execute a shell command as the Node.js application process. The impact is bounded by that process's filesystem, network, and service permissions. Applications that do not expose untrusted configuration or command arguments to simple-git are outside this threat model.

Affected versions

Commit 6b3c631eadea81f80ed10f6dec7d19a9db4d7084 introduced the default unsafe-operation plugin, and [email protected] is the first release confirmed to contain it. Its implementation only rejected protocol.allow configuration, leaving trailer-command configuration unblocked.

The latest simple-git release, 3.36.0, still lacks a trailer-command matcher. The current main branch also lacks one. No released remediation was identified.

Remediation

Default-deny configuration keys that can trigger executable behavior, or add a dedicated unsafe category that rejects trailer.<token>.cmd before spawning Git unless the application explicitly opts in.

Evaluate trailer.<token>.command alongside .cmd, because Git documents it as related command behavior. Add parser and integration tests for leading -c, configured instance prefixes, and git config write forms, asserting that no Git child process is spawned without an explicit unsafe opt-in.

Evidence

  • [email protected] was released on 2022-11-12 and contains the initial unsafe-operation plugin.
  • [email protected] was released on 2026-04-12; its parser source does not match trailer.<token>.cmd.
  • main retains the missing matcher in packages/argv-parser/src/vulnerabilities/detect-vulnerable-config-writes.ts.
  • Git v2.39.5 documents the trailer command behavior in Documentation/git-interpret-trailers.txt.
  • PR #1167 expanded other configuration checks but did not add a trailer-command matcher and is not release-backed as a remediation.
  • This review verified repository, release, and source artifacts through GitHub; it did not independently execute the runtime reproduction.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmsimple-git≥ 3.15.0&&< 4.0.14.0.1npm install simple-git@4.0.1

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update simple-git to 4.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-102828 is resolved across your whole dependency graph.

  3. Workarounds

    Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

## 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 <key>=<value>`. ## Summary `trailer.<token>.cmd` is not recognized as unsafe by the default guard. Therefore, a configured inline value reaches Git without a `GitPluginError`. Git documents `trailer.<token>.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
O3 Security · Impact-Aware SCA

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CVE-2026-102828: simple-git — Fixed in 4.0.1