{"schema":"threatline.record/2","record":{"id":"CVE-2026-102828","aliases":["GHSA-x6jw-m9v5-85vh"],"summary":"simple-git unsafe-operation guard does not block trailer command configuration","details":"## Affected product\n\nThe 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>`.\n\n## Summary\n\n`trailer.<token>.cmd` is not recognized as unsafe by the default guard. Therefore, a configured inline value reaches Git without a `GitPluginError`.\n\nGit 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.\n\n## Technical details\n\n`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.\n\nIn `simple-git@3.36.0`, `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.\n\nGit 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.\n\n## Preconditions\n\nThe 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`.\n\nThe 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.\n\n## Verification\n\nUse an isolated test environment and a harmless executable test helper that records only its invocation.\n\n**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`.\n\n**Bypass:** Configure `trailer.audit.cmd=<test-helper>` through the same option and invoke Git with the equivalent argv shape:\n\n`git -c trailer.audit.cmd=<test-helper> interpret-trailers --trailer audit:<value> <input-file>`\n\nA vulnerable build does not raise `GitPluginError`; Git invokes the test helper while processing the trailer. Confirm the helper invocation, then remove test artifacts.\n\n## Impact\n\nAn 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.\n\n## Affected versions\n\nCommit `6b3c631eadea81f80ed10f6dec7d19a9db4d7084` introduced the default unsafe-operation plugin, and `simple-git@3.15.0` is the first release confirmed to contain it. Its implementation only rejected `protocol.allow` configuration, leaving trailer-command configuration unblocked.\n\nThe 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.\n\n## Remediation\n\nDefault-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.\n\nEvaluate `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.\n\n## Evidence\n\n- `simple-git@3.15.0` was released on 2022-11-12 and contains the initial unsafe-operation plugin.\n- `simple-git@3.36.0` was released on 2026-04-12; its parser source does not match `trailer.<token>.cmd`.\n- `main` retains the missing matcher in `packages/argv-parser/src/vulnerabilities/detect-vulnerable-config-writes.ts`.\n- Git v2.39.5 documents the trailer command behavior in `Documentation/git-interpret-trailers.txt`.\n- PR #1167 expanded other configuration checks but did not add a trailer-command matcher and is not release-backed as a remediation.\n- This review verified repository, release, and source artifacts through GitHub; it did not independently execute the runtime reproduction.","categories":["Libraries & packages"],"product":"simple-git","vendor":"steveukx","ecosystem":"npm","affected_ranges":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-x6jw-m9v5-85vh","source_modified_at":"2026-10-05T23:48:14Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"simple-git"},"range":">= 3.15.0, < 4.0.1"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-102828","source_modified_at":"2026-09-30T20:08:15.246Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"git-js","vendor":"steveukx","versions":[{"status":"affected","version":">= 3.15.0, < 4.0.1"}],"defaultStatus":null},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-x6jw-m9v5-85vh","source_modified_at":"2026-10-06T00:00:09.444607978Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"simple-git","ecosystem":"npm","purl":"pkg:npm/simple-git"},"ranges":[{"type":"SEMVER","events":[{"introduced":"3.15.0"},{"fixed":"4.0.1"}]}],"versions":[]}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-x6jw-m9v5-85vh","source_modified_at":"2026-10-05T23:48:14Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"simple-git"},"version":"4.0.1"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-x6jw-m9v5-85vh","source_modified_at":"2026-10-06T00:00:09.444607978Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"simple-git","ecosystem":"npm","purl":"pkg:npm/simple-git"},"version":"4.0.1"}],"cvss":9.2,"severity":"Critical","kev":{"listed":false},"epss":{"probability":0.00375,"percentile":0.30251,"score_date":"2026-10-23"},"published_at":"2026-09-29T18:43:19.086Z","modified_at":"2026-10-06T00:00:09.444607978Z","provenance":[{"source":"GitHub Advisory Database","url":"https://github.com/advisories/GHSA-x6jw-m9v5-85vh","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-05T23:48:14Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-102828","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-09-30T20:08:15.246Z"},{"source":"OSV","url":"https://osv.dev/vulnerability/GHSA-x6jw-m9v5-85vh","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-06T00:00:09.444607978Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-102828","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["GitHub Advisory Database","CVE List","OSV","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/steveukx/git-js/security/advisories/GHSA-x6jw-m9v5-85vh","tags":["x_refsource_CONFIRM"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-102828","source":"GitHub Advisory Database"},{"source":"CVE List","url":"https://github.com/steveukx/git-js/pull/1198","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/steveukx/git-js/commit/d762810c13b331ff1e5eb24c0b434646d2a8d1b3","tags":["x_refsource_MISC"]},{"source":"CVE List","url":"https://github.com/steveukx/git-js/releases/tag/simple-git@4.0.1","tags":["x_refsource_MISC"]},{"url":"https://github.com/advisories/GHSA-x6jw-m9v5-85vh","source":"GitHub Advisory Database"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"total","assessed_at":"2026-09-30T20:08:07.142494Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"ecosystem","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-06T00:00:09.444607978Z","content_hash":"cfa0fd324007a551846c86e02e0b127829a84ad66870456c3b97860a49098b01"}}