What’s Vulnerable › Vulnerabilities

CVE-2025-7339: on-headers vulnerable to http response header manipulation

• Severity: low (CVSS 3.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-07-17 · updated 2026-06-17
• Weakness: CWE-241

Description

on-headers is a node.js middleware for listening to when a response writes headers. A bug in on-headers versions `<1.1.0` may result in response headers being inadvertently modified when an array is passed to `response.writeHead()`. Users should upgrade to version 1.1.0 to receive a patch. Uses are strongly encouraged to upgrade to `1.1.0`, but this issue can be worked around by passing an object to `response.writeHead()` rather than an array.

Affected products

• Npm On-Headers: before 1.1.0 — fixed in 1.1.0
• jshttp on-headers: before 1.1.0 — fixed in 1.1.0

How to fix

Upgrade to a fixed version: Npm On-Headers 1.1.0; jshttp on-headers 1.1.0. Check the vendor advisory for mitigations.

References

• https://cna.openjsf.org/security-advisories.html
• https://github.com/expressjs/morgan/issues/315
• https://github.com/jshttp/on-headers/commit/c6e384908c9c6127d18831d16ab0bd96e1231867
• https://github.com/jshttp/on-headers/issues/15
• https://github.com/jshttp/on-headers/security/advisories/GHSA-76c9-3jph-rj3q

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