A high-severity command injection vulnerability, CVE-2026-9277, was disclosed in the Node.js package shell-quote affecting versions through 1.8.3. The flaw is in quote(), which escaped attacker-influenced object-token .op values character by character using a JavaScript regex that does not match line terminators. Because POSIX shells treat newlines as command separators, a crafted .op containing \n, \r, U+2028, or U+2029 could cause a second command to run when the resulting string was passed to /bin/sh.
The issue is narrower than a typical shell injection because exploitation requires applications to use documented object tokens, either directly or through parse(cmd, envFn) when envFn returns an object with an attacker-controlled .op field. A proof of concept showed that injected content could trigger execution of a follow-on command such as id. Version 1.8.4 fixes the bug by replacing arbitrary escaping with strict validation and allowlisting of valid operators, and by blocking line terminators in related token fields such as glob patterns and comments.

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The vulnerability was publicly disclosed on 2026-05-22 with details explaining that unescaped line terminators in .op could let POSIX shells treat injected newlines as command separators and execute a second command. Public reporting included proof-of-concept behavior and noted affected versions up to and including 1.8.3.
On 2026-05-22, shell-quote version 1.8.4 was released to fix the vulnerability by replacing arbitrary .op escaping with strict validation and allowlisting of valid operator values. The fix also forbade line terminators in related token fields such as glob patterns and comments.
A command injection vulnerability in the shell-quote package, later assigned CVE-2026-9277, was reported on 2026-05-09. The flaw affected quote() when applications passed object tokens with attacker-influenced .op values.
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