# CVE-2026-77776: Headroom LLM proxy authentication bypass via x-headroom-user-id header

Source: https://junglewise.ai/threats/cve-2026-77776-headroom-llm-proxy-authentication-bypass-via-x-headroom-user-id  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-21. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77776 · Severity: critical · CVSS 9.1 · Published 2026-08-21

Headroom is an LLM proxy service that compresses data before sending it to language models. The proxy fails to authenticate the x-headroom-user-id request header, allowing an attacker to impersonate any user and read or modify other users' stored LLM conversation history. Default Docker deployments expose this vulnerability to the network without authentication.

Technologies: [Headroom Labs Headroom](https://junglewise.ai/threats/technologies/headroom). Vendors: [Headroom Labs](https://junglewise.ai/threats/vendors/headroom-labs).

## Quick answers

**Is CVE-2026-77776 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77776 being exploited in the wild.

**How severe is CVE-2026-77776?** Critical severity, with a CVSS score of 9.1, published 21 August 2026.

**Which products and versions are affected?** Headroom Labs Headroom <0.9.0.

**Is there a fix for CVE-2026-77776?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-77776 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-77776?** Check whether you run Headroom Labs Headroom at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an authentication bypass in Headroom's OpenAI-compatible proxy. The x-headroom-user-id header is read directly in headroom/proxy/handlers/openai.py (chat completion and websocket paths) without binding it to the actual caller's identity. An unauthenticated network attacker can craft requests with arbitrary user identifiers to access or modify other users' memory storage. The fix introduces identity validation through a resolve_memory_identity seam that honors the header only for loopback or allowlisted callers, otherwise binding identity to proxy-token fingerprint or OS user. Default Docker Compose configuration ships with --host 0.0.0.0, no HEADROOM_PROXY_TOKEN enforcement, and published ports, exposing data-plane routes to the network without authentication.

## Affected products

- Headroom Labs Headroom <0.9.0

## Timeline

- 2026-08-21: disclosed

## References

- [https://pypi.org/](https://pypi.org/)
- [https://github.com/headroomlabs-ai/headroom](https://github.com/headroomlabs-ai/headroom)

## Related threats

- [Headroom Cross-Site WebSocket Hijacking in proxy server](https://junglewise.ai/threats/cve-2026-71416-headroom-cross-site-websocket-hijacking-in-proxy-server)
- [Headroom LLM proxy SSRF via x-headroom-base-url header](https://junglewise.ai/threats/cve-2026-77775-headroom-llm-proxy-ssrf-via-x-headroom-base-url-header)