CVE-2026-9277 ljharb CVE debrief

Who should care

Developers and users of the shell-quote package should be aware of this vulnerability. The vulnerability can be exploited by constructing a malicious object or via the `parse()` function. Users should update to the latest version of the package to mitigate the vulnerability.

Technical summary

The `quote()` function in the shell-quote package did not validate object-token inputs against the operator model used by `parse()`. This allows an attacker to inject malicious commands. The vulnerability can be exploited in two ways: directly constructing a malicious object or via the `parse()` function when an attacker-influenced environment function is used. The vulnerability has been fixed by replacing the per-character escape with strict shape validation. The fixed version validates the `.op` field against a control-operator allowlist and forbids line terminators.

Defensive priority

High

Recommended defensive actions

• Update to the latest version of the shell-quote package
• Validate user input to prevent malicious object construction
• Use a secure environment function with the `parse()` function
• Monitor for suspicious activity
• Implement compensating controls to detect and prevent exploitation

Evidence notes

The vulnerability was reported by an unknown vendor and has a low confidence level. The CVE record was published on May 22, 2026, and modified on July 1, 2026. The NVD detail page provides additional information about the vulnerability.

Official resources