CVE-2026-77776

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreHIGH confidence

Score 9.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-21. a secondary CVSS source baseline 9.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: ghsa, secondary
Trending — 3 sources updated this week
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 9.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.1
EG Score
9.1(high)
EG Risk
56(Track)
EG Risk 56/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
—
EPSS %ILE
—
KEV
Not listed

Published

August 21, 2026

Last Modified

August 21, 2026

Advisory Details (5)

Auto-updated Aug 21, 2026
Patch available. Sources: github_pr.
generic

Headroom Proxy Treats the Client-Supplied x-headroom-user-id Header as an Authenticated Identity | Advisories | VulnCheck

https://www.vulncheck.com/advisories/headroom-proxy-treats-the-client-supplied-x-headroom-user-id-header-as-an-authenticated-identity
generic Patch Available

GitHub - headroomlabs-ai/headroom: Compress tool outputs, logs, files, and RAG chunks before they reach the LLM. 20% fewer tokens for coding agents, 60-95% fewer tokens for JSON, same answers. Library, proxy, MCP server. · GitHub

https://github.com/headroomlabs-ai/headroom
generic

headroom/headroom/proxy/identity.py at v0.36.1 · headroomlabs-ai/headroom · GitHub

https://github.com/headroomlabs-ai/headroom/blob/v0.36.1/headroom/proxy/identity.py
generic

headroom/headroom/proxy/handlers/openai.py at v0.29.0 · headroomlabs-ai/headroom · GitHub

https://github.com/headroomlabs-ai/headroom/blob/v0.29.0/headroom/proxy/handlers/openai.py
github_pr

security: address u9up assessment findings (WEB-01–07)

Fix merged in headroomlabs-ai/headroom PR #2207 on 2026-08-20 — awaiting tagged release

https://github.com/headroomlabs-ai/headroom/pull/2207

Vendor Advisories for CVE-2026-77776(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 10× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-21 22:25 UTCEG score recompute
  2. 2026-08-21 22:25 UTCGHSA enrichment
  3. 2026-08-21 21:52 UTCEG score recompute
  4. 2026-08-21 21:52 UTCGHSA enrichment
  5. 2026-08-21 19:39 UTCGHSA enrichment
  6. 2026-08-21 15:59 UTCEG score recompute
  7. 2026-08-21 15:59 UTCGHSA enrichment
  8. 2026-08-21 12:19 UTCEG score recompute
  9. 2026-08-21 11:30 UTCEG score recompute
  10. 2026-08-21 11:29 UTCMITRE cvelistV5first tracked

Frequently asked(4)

What is CVE-2026-77776?
CVE-2026-77776 is a critical vulnerability published on August 21, 2026. 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…
When was CVE-2026-77776 disclosed?
CVE-2026-77776 was first published in the National Vulnerability Database on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-77776?
CVE-2026-77776 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-77776?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77776, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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