CVE-2026-52845

HIGHPre-NVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 84% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
8.1
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 8.1Exploit: NoneExposed: 0

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

Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forward_auth copy_headers deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through php_fastcgi, Caddy normalizes HTTP headers into CGI variables by replacing - with _. This lets a client send an underscore alias that survives the forward_auth delete step but becomes the same PHP/FastCGI variable. Result: a remote client can inject or sometimes override identity/group headers trusted by PHP/FastCGI applications behind Caddy. This vulnerability is fixed in 2.11.4.

CVSS v3
8.1
EG Score
8.1(medium)
EPSS
15.8%
KEV
Not listed

Published

June 16, 2026

Last Modified

June 30, 2026

Advisory Details (1)

Auto-updated Jun 23, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

FastCGI header normalization bypass in `forward_auth copy_headers` · Advisory · caddyserver/caddy · GitHub

https://github.com/caddyserver/caddy/security/advisories/GHSA-f59h-q822-g45g

Vendor Advisories for CVE-2026-52845(1)

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

Affected Packages

(2 across 1 ecosystem)
Go(2)
PackageVulnerable rangeFixed inDependents
github.com/caddyserver/caddy———
github.com/caddyserver/caddy/v2—2.11.4—

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 20× in last 7d / 54× 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. 2026-07-06 22:58 UTCEG score recompute
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 16:27 UTCEPSS rescore
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-06 02:23 UTCEPSS rescore
  6. 2026-07-05 22:50 UTCEG score recompute
  7. 2026-07-05 10:15 UTCEG score recompute
  8. 2026-07-05 02:30 UTCEPSS rescore
  9. 2026-07-04 21:34 UTCEG score recompute
  10. 2026-07-04 08:59 UTCEG score recompute
  11. 2026-07-04 06:31 UTCEPSS rescore
  12. 2026-07-03 20:15 UTCEG score recompute
  13. 2026-07-03 07:41 UTCEG score recompute
  14. 2026-07-02 19:06 UTCEG score recompute
  15. 2026-07-02 06:28 UTCEG score recompute
  16. 2026-07-01 17:52 UTCEG score recompute
  17. 2026-07-01 15:07 UTCEPSS rescore
  18. 2026-07-01 05:16 UTCEG score recompute
  19. 2026-06-30 23:22 UTCEPSS rescore
  20. 2026-06-30 16:41 UTCEG score recompute
  21. 2026-06-30 04:06 UTCEG score recompute
  22. 2026-06-29 15:30 UTCEG score recompute
  23. 2026-06-29 14:06 UTCEPSS rescore
  24. 2026-06-29 14:06 UTCEPSS rescore
  25. 2026-06-29 02:47 UTCEG score recompute
Show 29 more
  1. 2026-06-28 14:12 UTCEG score recompute
  2. 2026-06-28 14:07 UTCEPSS rescore
  3. 2026-06-28 04:56 UTCEPSS rescore
  4. 2026-06-28 04:56 UTCEPSS rescore
  5. 2026-06-28 01:37 UTCEG score recompute
  6. 2026-06-27 13:02 UTCEG score recompute
  7. 2026-06-27 03:08 UTCEPSS rescore
  8. 2026-06-27 00:26 UTCEG score recompute
  9. 2026-06-26 11:49 UTCEG score recompute
  10. 2026-06-25 21:29 UTCEG score recompute
  11. 2026-06-25 13:49 UTCEPSS rescore
  12. 2026-06-25 08:54 UTCEG score recompute
  13. 2026-06-24 20:19 UTCEG score recompute
  14. 2026-06-24 14:05 UTCEPSS rescore
  15. 2026-06-24 07:45 UTCEG score recompute
  16. 2026-06-23 18:23 UTCEG score recompute
  17. 2026-06-23 05:47 UTCEG score recompute
  18. 2026-06-22 17:00 UTCEG score recompute
  19. 2026-06-22 03:49 UTCEG score recompute
  20. 2026-06-21 15:12 UTCEG score recompute
  21. 2026-06-21 02:36 UTCEG score recompute
  22. 2026-06-20 13:59 UTCEG score recompute
  23. 2026-06-20 01:24 UTCEG score recompute
  24. 2026-06-19 12:42 UTCEG score recompute
  25. 2026-06-19 00:07 UTCEG score recompute
  26. 2026-06-18 11:32 UTCEG score recompute
  27. 2026-06-17 22:53 UTCEG score recompute
  28. 2026-06-17 10:19 UTCEG score recompute
  29. 2026-06-16 21:44 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-52845?
CVE-2026-52845 is a high vulnerability published on June 16, 2026. Caddy is an extensible server platform that uses TLS by default. Prior to 2.11.4, forwardauth copyheaders deletes the exact client-supplied identity header before copying the trusted value from the auth gateway. But when the request later goes through phpfastcgi, Caddy normalizes HTTP headers into…
When was CVE-2026-52845 disclosed?
CVE-2026-52845 was first published in the National Vulnerability Database on June 16, 2026, with the most recent update on June 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-52845 actively exploited?
CVE-2026-52845 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 15.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-52845?
CVE-2026-52845 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-52845?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-52845, 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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