shell-quote's `quote()` function emits a `{ comment }` token as `#` followed by its text, which comments out the rest of the shell line, including the opening quote of any later string token

Overview

shell-quote's quote() function emits a { comment } token as # followed by its text, which comments out the rest of the shell line, including the opening quote of any later string token. A line terminator (\n, \r, U+2028, U+2029) in that later string therefore ends the comment, and the rest of the string is parsed as shell input: quote(['echo', 'ok', { comment: 'x' }, 'a\nid;#']) runs id in sh, bash, dash, ksh and zsh. parse() emits a comment token for a # in the middle of a word (for example http://example.com/#frag), so callers that combine parse() output with another untrusted string, such as quote(parse(untrustedCommand).concat(untrustedArg)), are affected. The fix for CVE-2026-9277 rejected line terminators in the comment's own text, but not in the tokens after it. Fixed in 1.11.0: quote() throws a TypeError when a string after a { comment } token contains a line terminator.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.