CVE-2026-9277
ADVISORY - githubSummary
Summary
shell-quote's quote() function did not validate object-token inputs against the operator model used by parse(). The .op field was backslash-escaped character by character using /(.)/g, which in JavaScript does not match line terminators (\n, \r, U+2028, U+2029). A line terminator in .op therefore passed through unescaped into the output; POSIX shells treat a literal \n as a command separator, so any content after it would execute as a second command.
The vulnerable code path is reachable in two ways. Neither requires the parser to misbehave — parse() only emits ops from a fixed control set — but both are documented API surface:
- Direct construction. A caller builds
{ op: '...\n...' }from external input (e.g. a deserialized argument array) and passes it toquote(). envFnreturn.parse(cmd, envFn)is documented to splice the return value ofenvFninto the result array when it is an object. An attacker-influenced data source consulted byenvFncan introduce an object token whose.opreachesquote().
Impact
Shell command injection in callers that pass object tokens with attacker-influenced .op values to quote() and then hand the result to a shell. The preconditions are narrower than ordinary string injection — they require the caller to feed object tokens into quote() — but object tokens are a public, documented part of the API surface, and quote() is intended to be a shell-safety boundary.
PoC
const { parse, quote } = require('shell-quote');
// Direct construction
quote([{ op: ';\nid' }]);
// → "\;\n\\i\\d" ← literal newline; second line executes as a command
// Via parse() with an envFn returning attacker-shaped objects
const tokens = parse('echo $X', () => ({ op: ';\nid' }));
require('child_process').execSync(quote(tokens), { shell: true });
// Executes `id` after `echo \;`.
Confirmed under sh, bash, dash, and zsh.
Patch
Fixed by replacing the per-character escape with strict shape validation in quote(). The object-token branch now:
{ op }—.opmust be a string from the same allowlist the parser emits (||,&&,;;,|&,<(,<<<,>>,>&,<&,&,;,(,),|,<,>). Anything else throwsTypeError. This is the direct fix for the reported issue and removes the entire class of.opinjection.{ op: 'glob', pattern }—.patternmust be a string with no line terminators. Glob metacharacters (*,?,[,],{,},,) pass through; all other shell-special characters are backslash-escaped. (Previously the pattern field was discarded entirely and the literal string\g\l\o\bwas emitted — a latent bug, not security-relevant.){ comment }—.commentmust be a string with no line terminators (line terminators would end the shell comment and resume command parsing — same injection shape).- Any other object shape —
TypeError.
The fix is allowlist-based rather than a targeted regex tweak, so it closes the reported vector and forecloses adjacent ones (U+2028 / U+2029 line separators in .op, line terminators in comments, unknown-shape objects coerced through .replace).
Workarounds
Prior to upgrading, callers that build object tokens from untrusted input should validate .op against the parser's operator set themselves, and never construct { op } from attacker-controlled strings.
Credits
Reported by Akshat Sinha
GitHub
CVSS SCORE
9.2critical| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| shell-quote | npm | - | - | >=1.1.0,<=1.8.3 | 1.8.4 |
CVSS:4 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: A race condition must be won to successfully exploit the vulnerability. The successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker. The attack may need to be launched multiple times against a single target before being successful. Network injection. The attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges.
There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the Vulnerable System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Vulnerable System.
There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the Vulnerable System (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).
There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
NIST
CVSS SCORE
9.2criticalDebian
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Ubuntu
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CVSS SCORE
N/AmediumChainguard
CGA-qhgj-wh56-w944
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minimos
MINI-9q99-vmjw-hjxw
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minimos
MINI-c98h-4vqh-8jrm
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minimos
MINI-hg4r-84vf-w9rp
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minimos
MINI-m2r9-43xq-wxjm
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minimos
MINI-v87r-r2cf-c3x3
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