CVE-2026-52845: Caddy is an extensible server platform that uses TLS by default

Q: How do I fix CVE-2026-52845?

caddy: upgrade to 2.11.4. Exact commands for each OS are on this page.

Q: Is CVE-2026-52845 being exploited?

CVE-2026-52845 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-52845 affect?

CVE-2026-52845 affects caddy. Severity is high (CVSS 8.1). 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

Q: How urgent is CVE-2026-52845?

Priority 43/100. High severity; Public exploit reference

This month

HIGH 8.1UPGRADE

CVE-2026-52845 is a high-severity flaw (CVSS 8.1) affecting caddy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-287, CWE-290, CWE-444
Published	2026-06-23
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: caddyserver

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-23 18:18 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

caddyserver caddy UPGRADE

Affected: < 2.11.4

Fixed in: 2.11.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy caddy || rpm -q caddy || caddy --version

2. UPGRADE to 2.11.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade caddy

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade caddy

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-52845?

caddy: upgrade to 2.11.4. Exact commands for each OS are on this page.

Is CVE-2026-52845 being exploited?

CVE-2026-52845 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-52845 affect?

CVE-2026-52845 affects caddy. Severity is high (CVSS 8.1). 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

How urgent is CVE-2026-52845?

Priority 43/100. High severity; Public exploit reference

Software pages

PHP vulnerabilities · Caddy vulnerabilities

Related CVEs

CVE-2026-45135 HIGH 8.1 UPGRADE Caddy is an extensible server platform that uses TLS by default
CVE-2026-52844 HIGH 7.5 UPGRADE Caddy is an extensible server platform that uses TLS by default
CVE-2026-45692 MEDIUM 5.4 UPGRADE Caddy is an extensible server platform that uses TLS by default

References

← Back to latest CVEs