# CVE-2026-77776: Headroom Proxy Treats the Client-Supplied x-headroom-user-id Header as an Authenticated Identity

Status: published. Published: 2026-08-21. Updated: 2026-11-08.

Headroom's LLM proxy derives the memory owner from the x-headroom-user-id request header. The header is read directly at several points in headroom/proxy/handlers/openai.py, including the chat completion and websocket paths, and nothing binds the value to the caller. A client can therefore name another user's identifier and read or write that user's stored LLM memory. The fix introduces a single resolve_memory_identity seam in headroom/proxy/identity.py that honors the header only for loopback or allowlisted callers and otherwise binds the identity to the proxy-token fingerprint or the operating system user. The pip console script binds 127.0.0.1 by default, but the reference docker-compose.yml ships --host 0.0.0.0 with published ports and no required HEADROOM_PROXY_TOKEN, which the server itself warns about at startup, so a deployment following the shipped compose exposes the affected data-plane routes to the network without authentication.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/headroomlabs-ai/headroom/pull/2207

## Affected products and versions

- Headroom Labs / Headroom (headroom-ai): ≥ 0; < 0.36.1 (affected, semver); 0.36.1 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 3.1: 9.1 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N; source: CNA: VulnCheck

- CVSS 4.0: 9.3 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.61% as of 2026-11-08; percentile 49.61%

- SSVC: exploitation none; automatable yes; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-639

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/headroomlabs-ai/headroom/pull/2207 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/headroomlabs-ai/headroom/blob/v0.29.0/headroom/proxy/handlers/openai.py (CNA: VulnCheck; technical-description)

- https://github.com/headroomlabs-ai/headroom/blob/v0.36.1/headroom/proxy/identity.py (CNA: VulnCheck; technical-description)

- https://github.com/headroomlabs-ai/headroom (CNA: VulnCheck; product)

- https://www.vulncheck.com/advisories/headroom-proxy-treats-the-client-supplied-x-headroom-user-id-header-as-an-authenticated-identity (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-77776; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-77776; retrieved 2026-11-08; source updated Not reported

Revision: 5227f425a8353edcc7dea99a46e88c82b53907de612ab480c08e452d2c911575

Canonical: https://y2.dev/cve/CVE-2026-77776

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