CVE-2026-77776

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM 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: epss, 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: 0%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(medium)
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
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 21, 2026

Last Modified

September 9, 2026

Advisory Details (5)

Auto-updated Sep 15, 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
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
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
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

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 56× in last 7d / 239× 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.

Showing the most recent 100 of 251 total refreshes for this CVE.

  1. 2026-09-21 03:18 UTCGHSA enrichment
  2. 2026-09-20 23:38 UTCEG score recompute
  3. 2026-09-20 23:38 UTCGHSA enrichment
  4. 2026-09-20 20:16 UTCEPSS rescore
  5. 2026-09-20 19:58 UTCGHSA enrichment
  6. 2026-09-20 16:18 UTCGHSA enrichment
  7. 2026-09-20 12:37 UTCEG score recompute
  8. 2026-09-20 12:37 UTCGHSA enrichment
  9. 2026-09-20 08:55 UTCGHSA enrichment
  10. 2026-09-20 03:24 UTCGHSA enrichment
  11. 2026-09-19 23:43 UTCGHSA enrichment
  12. 2026-09-19 20:04 UTCGHSA enrichment
  13. 2026-09-19 16:23 UTCEG score recompute
  14. 2026-09-19 16:23 UTCGHSA enrichment
  15. 2026-09-19 12:43 UTCGHSA enrichment
  16. 2026-09-19 09:02 UTCGHSA enrichment
  17. 2026-09-19 04:57 UTCGHSA enrichment
  18. 2026-09-19 01:17 UTCGHSA enrichment
  19. 2026-09-18 21:37 UTCEG score recompute
  20. 2026-09-18 21:37 UTCGHSA enrichment
  21. 2026-09-18 19:28 UTCEPSS rescore
  22. 2026-09-18 16:32 UTCGHSA enrichment
  23. 2026-09-18 12:05 UTCGHSA enrichment
  24. 2026-09-18 08:25 UTCGHSA enrichment
  25. 2026-09-18 04:37 UTCGHSA enrichment
Show 75 more
  1. 2026-09-18 00:57 UTCGHSA enrichment
  2. 2026-09-17 21:17 UTCEG score recompute
  3. 2026-09-17 21:17 UTCGHSA enrichment
  4. 2026-09-17 14:43 UTCGHSA enrichment
  5. 2026-09-17 10:53 UTCGHSA enrichment
  6. 2026-09-17 07:07 UTCGHSA enrichment
  7. 2026-09-17 03:27 UTCGHSA enrichment
  8. 2026-09-16 23:22 UTCGHSA enrichment
  9. 2026-09-16 19:42 UTCGHSA enrichment
  10. 2026-09-16 14:20 UTCEG score recompute
  11. 2026-09-16 14:20 UTCGHSA enrichment
  12. 2026-09-16 14:08 UTCEPSS rescore
  13. 2026-09-16 09:37 UTCEG score recompute
  14. 2026-09-16 09:37 UTCGHSA enrichment
  15. 2026-09-16 05:15 UTCEPSS rescore
  16. 2026-09-16 04:39 UTCGHSA enrichment
  17. 2026-09-16 00:49 UTCGHSA enrichment
  18. 2026-09-15 21:07 UTCGHSA enrichment
  19. 2026-09-15 17:16 UTCGHSA enrichment
  20. 2026-09-15 13:36 UTCGHSA enrichment
  21. 2026-09-15 09:56 UTCGHSA enrichment
  22. 2026-09-15 06:16 UTCEG score recompute
  23. 2026-09-15 06:16 UTCGHSA enrichment
  24. 2026-09-15 03:12 UTCEPSS rescore
  25. 2026-09-15 03:12 UTCEPSS rescore
  26. 2026-09-15 02:32 UTCGHSA enrichment
  27. 2026-09-14 22:46 UTCGHSA enrichment
  28. 2026-09-14 19:06 UTCGHSA enrichment
  29. 2026-09-14 15:20 UTCGHSA enrichment
  30. 2026-09-14 11:38 UTCGHSA enrichment
  31. 2026-09-14 07:58 UTCGHSA enrichment
  32. 2026-09-14 04:18 UTCGHSA enrichment
  33. 2026-09-14 00:38 UTCGHSA enrichment
  34. 2026-09-13 20:58 UTCGHSA enrichment
  35. 2026-09-13 17:18 UTCEG score recompute
  36. 2026-09-13 17:18 UTCGHSA enrichment
  37. 2026-09-13 13:38 UTCGHSA enrichment
  38. 2026-09-13 09:58 UTCGHSA enrichment
  39. 2026-09-13 06:18 UTCGHSA enrichment
  40. 2026-09-13 02:38 UTCGHSA enrichment
  41. 2026-09-12 22:58 UTCGHSA enrichment
  42. 2026-09-12 19:18 UTCGHSA enrichment
  43. 2026-09-12 15:38 UTCEG score recompute
  44. 2026-09-12 15:38 UTCGHSA enrichment
  45. 2026-09-12 11:58 UTCGHSA enrichment
  46. 2026-09-12 08:17 UTCGHSA enrichment
  47. 2026-09-12 04:37 UTCGHSA enrichment
  48. 2026-09-12 00:57 UTCGHSA enrichment
  49. 2026-09-11 21:17 UTCGHSA enrichment
  50. 2026-09-11 17:37 UTCEG score recompute
  51. 2026-09-11 17:37 UTCGHSA enrichment
  52. 2026-09-11 14:53 UTCEPSS rescore
  53. 2026-09-11 13:57 UTCGHSA enrichment
  54. 2026-09-11 10:17 UTCEG score recompute
  55. 2026-09-11 10:17 UTCGHSA enrichment
  56. 2026-09-11 06:34 UTCGHSA enrichment
  57. 2026-09-11 02:54 UTCGHSA enrichment
  58. 2026-09-10 23:14 UTCGHSA enrichment
  59. 2026-09-10 19:33 UTCGHSA enrichment
  60. 2026-09-10 15:53 UTCGHSA enrichment
  61. 2026-09-10 12:13 UTCEG score recompute
  62. 2026-09-10 12:13 UTCGHSA enrichment
  63. 2026-09-10 09:35 UTCEPSS rescore
  64. 2026-09-10 08:05 UTCGHSA enrichment
  65. 2026-09-10 04:25 UTCGHSA enrichment
  66. 2026-09-10 00:45 UTCGHSA enrichment
  67. 2026-09-09 20:50 UTCGHSA enrichment
  68. 2026-09-09 17:04 UTCGHSA enrichment
  69. 2026-09-09 12:59 UTCGHSA enrichment
  70. 2026-09-09 09:14 UTCGHSA enrichment
  71. 2026-09-09 05:34 UTCGHSA enrichment
  72. 2026-09-09 01:48 UTCEG score recompute
  73. 2026-09-09 01:48 UTCGHSA enrichment
  74. 2026-09-08 22:01 UTCEPSS rescore
  75. 2026-09-08 06:11 UTCGHSA enrichment

Related CVEs(same CWE)

Frequently asked(5)

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, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77776 actively exploited?
CVE-2026-77776 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 71.9% of all scored CVEs.
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.

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