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 79% 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%CVSS: 8.1Exploit: Elevated riskExposed: 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)
EG Risk
52(Track*)
EG Risk 52/100SSVC: 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
Severity81% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
21%
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.
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

(5 across 4 ecosystems)
Go(2)
PackageVulnerable rangeFixed inDependents
github.com/caddyserver/caddy———
github.com/caddyserver/caddy/v2—2.11.4—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
caddy2.11.2-1 ... 2.6.2-9 (14 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
caddy2.11.2-1 ... 2.6.2-14 (6 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
caddy2.11.2-1, 2.11.2-1~bpo13+1, 2.6.2-12, 2.6.2-13, 2.6.2-142.11.4-1—

Weakness Classification(3)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 48× 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. 2026-08-25 13:49 UTCEPSS rescore
  2. 2026-08-24 23:22 UTCEG score recompute
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  1. 2026-08-09 23:49 UTCEG score recompute
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  68. 2026-06-25 13:49 UTCEPSS rescore
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  70. 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 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% probability of exploitation in the next 30 days, which ranks it in the top 78.9% of all scored CVEs.
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.

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