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: 0.3%, top 78% 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
Elevated
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 8.1Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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
8.1HIGHmedium confidence
EG Risk
52
EG Risk 52/100

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
Severity81% × 45%
Exploitation40% × 40%
Automatability0% × 15%
EPSS PROB
0.4%
EPSS %ILE
36th
KEV
Not listed

Published

June 16, 2026

Last Modified

July 15, 2026

Advisory Details (1)

Auto-updated Jun 23, 2026
🔬 Proof of concept available. Patch available. Sources: github.
githubMentions a patch (unverified)🟡 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

(5 across 4 ecosystems)
Go(2)
PackageVulnerable rangeFix by version rangeDependents
github.com/caddyserver/caddy—
  • every version through 1.0.5: no fix on record
—
github.com/caddyserver/caddy/v2—
  • every version up to 2.11.4: fixed in 2.11.4
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
caddy2.11.2-1 ... 2.6.2-9 (14 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
caddy2.6.2-12
  • every version up to 2.6.2-12+deb13u1: fixed in 2.6.2-12+deb13u1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
caddy2.11.2-1, 2.11.2-1~bpo13+1, 2.6.2-12, 2.6.2-13, 2.6.2-14
  • every version up to 2.11.4-1: fixed in 2.11.4-1
—

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 25× 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 133 total refreshes for this CVE.

  1. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
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  8. 2026-10-03 07:09 UTCOSV refresh
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  22. 2026-09-14 03:28 UTCEG score recompute
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  1. 2026-09-08 22:01 UTCEPSS rescore
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  8. 2026-08-30 22:42 UTCEG score recompute
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  15. 2026-08-24 23:22 UTCEG score recompute
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  24. 2026-08-18 13:48 UTCEPSS rescore
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  26. 2026-08-16 23:48 UTCEG score recompute
  27. 2026-08-16 14:56 UTCEPSS rescore
  28. 2026-08-16 11:13 UTCEG score recompute
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  39. 2026-08-09 23:49 UTCEG score recompute
  40. 2026-08-09 13:46 UTCEPSS rescore
  41. 2026-08-07 21:31 UTCEG score recompute
  42. 2026-08-06 20:22 UTCEG score recompute
  43. 2026-08-06 13:47 UTCEPSS rescore
  44. 2026-08-06 07:48 UTCEG score recompute
  45. 2026-08-05 19:17 UTCEPSS rescore
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  47. 2026-08-04 15:10 UTCEPSS rescore
  48. 2026-08-04 10:39 UTCEPSS rescore
  49. 2026-08-03 14:40 UTCEG score recompute
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  62. 2026-07-26 19:45 UTCEG score recompute
  63. 2026-07-26 14:54 UTCEPSS rescore
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  66. 2026-07-23 14:18 UTCEPSS rescore
  67. 2026-07-23 03:19 UTCEG score recompute
  68. 2026-07-22 14:08 UTCEPSS rescore
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  70. 2026-07-20 17:08 UTCEPSS rescore
  71. 2026-07-19 14:31 UTCEPSS rescore
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  73. 2026-07-19 02:29 UTCEPSS rescore
  74. 2026-07-18 10:04 UTCEPSS rescore
  75. 2026-07-16 17:03 UTCEPSS rescore

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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 on June 16, 2026, with the most recent update on July 15, 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 0.4% probability of exploitation in the next 30 days (36th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-52845?
CVE-2026-52845 has a CVSS base score of 8.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-52845?
A fix for CVE-2026-52845 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-52845 are linked in the Vendor Advisories panel on this page.

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