CVE-2026-52845
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 21% of all known CVEs.
References
Related Vulnerabilities
Other CWE-287 (Improper Authentication) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-35082 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2023-35078 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2017-7921 | Critical | 9.8 | 100% | KEV | - |
| CVE-2024-7593 | Critical | 9.8 | 100% | KEV | - |
| CVE-2023-46805 | High | 8.2 | 100% | KEV + Ransom | - |
| CVE-2022-40684 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
Common questions
How do I fix CVE-2026-52845?
Upgrade caddy on debian 13 to 2.6.2-12+deb13u1 or later.
Is CVE-2026-52845 being actively exploited?
Not that we know of. CVE-2026-52845 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.29% is the estimated probability that it will be exploited in the next 30 days. That is higher than 21% of all scored CVEs.
How severe is CVE-2026-52845?
CVE-2026-52845 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-52845 affect?
Published advisories record a fix for caddy (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-52845
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.