pillarjs cookies up to 0.9.1 Set-Cookie Header domain/path injection

Summaryinfo

A vulnerability, which was classified as critical, has been found in pillarjs cookies up to 0.9.1. This affects an unknown function of the component Set-Cookie Header. This manipulation of the argument domain/path causes injection. This vulnerability is registered as CVE-2026-88038. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in pillarjs cookies up to 0.9.1 and classified as critical. Affected by this vulnerability is an unknown functionality of the component Set-Cookie Header. The manipulation of the argument domain/path with an unknown input leads to a injection vulnerability. The CWE definition for the vulnerability is CWE-74. The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

cookies is a Node.js library for reading and writing HTTP cookies, used by Koa via ctx.cookies. In versions before 0.9.2 the library validates the cookie name and value against character sets that reject the semicolon separator, but the domain and path options are checked only against a permissive RFC 7230 field-content matcher that allows semicolons, and both are written into the Set-Cookie header unescaped. An application that passes untrusted or request-derived data into the domain or path option can therefore inject additional cookie attributes, overriding SameSite, Secure, HttpOnly, or Domain on the cookies the application issues. This is a Set-Cookie attribute injection issue (CWE-74). The issue is fixed in cookies 0.9.2, which validates domain and path against RFC 6265 character sets. As a workaround, keep domain and path application-set rather than derived from untrusted input.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-88038 since 09/09/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1055 for this issue.

Upgrading to version 0.9.2 eliminates this vulnerability.

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Productinfo

Vendor

• pillarjs

Name

• cookies

Version

• 0.9.0
• 0.9.1

Website

• Product: https://github.com/pillarjs/cookies/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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