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

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.<token>.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.

Source published

29 Sep 2026 18:43:19 UTC

Source modified

30 Sep 2026 20:08:15 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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.<token>.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.

Source published

Sep 29, 2026, 6:43:19 PM (timezone not stated)

Source modified

Sep 30, 2026, 8:08:15 PM (timezone not stated)

Observed here

9 Nov 2026 05:03:51 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

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.<token>.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.

Source published

29 Sep 2026 19:17:25 UTC

Source modified

8 Oct 2026 20:03:07 UTC

Observed here

25 Oct 2026 04:17:29 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

## 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.

Source published

5 Oct 2026 23:48:14 UTC

Source modified

6 Oct 2026 00:00:09 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · CRITICAL