Root cause
Injection & unsafe execution introduced
smart_user getUserDetails interpolates the caller-supplied username into a getent/grep shell string (commit fc358254).
AI-written code interpolated a caller-controlled username into a shell command executed via execAsync, allowing command substitution and arbitrary OS command execution as the server user.
How AI contributed: Direct introductionPublished Aug 14, 2026 in 
ooples/token-optimizer-mcpAll 2 findings in this repository
Show full advisory descriptionHide advisory description
CWE-78 OS command injection in smart_user get-user-info: caller-controlled username is interpolated into a POSIX shell string executed via child_process exec/execAsync (getent passwd "${username}" || grep "^${username}:" /etc/passwd). Double quotes do not prevent $(...) / backtick command substitution, so an MCP client can run arbitrary commands as the server user.
What actually happenedHide details
The smart_user get-user-info operation builds the Unix user lookup as a getent and grep command string and interpolates the caller-supplied username into it before running that string through execAsync. Double quotes do not stop command substitution, so a crafted username reaches the shell. The fix passes the username to getent as a separate argument through execFileSafe after assertSafeArg validation.
Fix
Security fix
The fix removes the shell-interpolated getent and grep pipeline, invokes getent with the username as a separate argv value through execFileSafe, and performs the passwd-file fallback in process.
Case facts
- CVE ID
- CVE-2026-55157
- GHSA ID
- GHSA-49MQ-FC6Q-3H46
- Published
- Aug 14, 2026
- Severity
- Not scored
- Language
- JavaScript
- AI tool
Claude- AI role
- Direct introduction
- Vulnerable release
- < 5.1.0
- Fixed release
- 5.1.0
AI-assisted change
AI-assisted changesrc/tools/system-operations/smart-user.tssource ooples/token-optimizer-mcp@fc3582544f+3−0
@@ -912,11 +912,14 @@ } } else { // Unix user details try {+ const { stdout: passwdOut } = await execAsync(+ `getent passwd "${username}" || grep "^${username}:" /etc/passwd`,+ ); const parts = passwdOut.trim().split(":"); if (parts.length < 7) {Show 5 hidden lines
throw new Error(`Invalid passwd entry for user: ${username}`); } } } }The AI-added getUserDetails branch builds the Unix user lookup as a shell string and interpolates the caller-supplied username into getent passwd and grep, so a crafted username reaches the shell (CWE-78).
Security fix
Fixsrc/tools/system-operations/smart-user.tssource ooples/token-optimizer-mcp@b4ee96dac7+58−0
@@ -706,8 +713,83 @@ export class SmartUser { // =========================== // Platform-Specific Methods // ===========================Show 5 hidden lines
+ /**+ * Read the full passwd database. Tries `getent passwd` (argv mode) and falls+ * back to reading /etc/passwd directly when getent is unavailable. Replaces+ * the former `getent passwd || cat /etc/passwd` shell pipeline.+ */+ private async readPasswdDatabase(): Promise<string> {+ try {+ const { stdout } = await execFileSafe('getent', ['passwd']);+ if (stdout.trim()) return stdout;+ } catch {+ // getent not available; fall through to the file read.Show 7 hidden lines
+ }+ return readFileSync('/etc/passwd', 'utf-8');+ }++ /**+ * Read the full group database. Tries `getent group` (argv mode) and falls+ * back to /etc/group. Replaces the former `getent group || cat /etc/group`.+ */+ private async readGroupDatabase(): Promise<string> {+ try {+ const { stdout } = await execFileSafe('getent', ['group']);+ if (stdout.trim()) return stdout;+ } catch {+ // getent not available; fall through to the file read.Show 9 hidden lines
+ }+ return readFileSync('/etc/group', 'utf-8');+ }++ /**+ * Look up a single passwd entry by username. Tries `getent passwd <user>`+ * (argv mode) and falls back to scanning /etc/passwd in-process. Replaces the+ * injectable `getent passwd "${username}" || grep "^${username}:" ...`.+ */+ private async lookupPasswdEntry(username: string): Promise<string> {+ assertSafeArg(username, 'username');+ try {+ const { stdout } = await execFileSafe('getent', ['passwd', username]);+ if (stdout.trim()) return stdout.trim();+ } catch {+ // fall through to file scanShow 17 hidden lines
+ }+ const contents = readFileSync('/etc/passwd', 'utf-8');+ const match = contents+ .split('\n')+ .find((line) => line.startsWith(`${username}:`));+ if (!match) {+ throw new Error(`User not found: ${username}`);+ }+ return match;+ }++ /**+ * Look up a single group entry by name. Tries `getent group <name>` (argv+ * mode) and falls back to scanning /etc/group. Replaces the injectable+ * `getent group "${groupname}" || grep "^${groupname}:" ...`.+ */+ private async lookupGroupEntry(groupname: string): Promise<string> {Replaces the shell-string interpolation of a caller-supplied username into getent/grep with an argv-based helper, removing the CWE-78 command-injection sink.
Patch fingerprints
AI-assisted change 0e12e71a62329d388a584586f82d3291f94b09a32328b025588c656d213d970f · Fix 68ecbe04a8399a33f2781fe570b880693fef731352dd383e489897847af0938b