CVE-2026-52845: CWE-287: Improper Authentication in caddyserver caddy
CVE-2026-52845 is an improper authentication vulnerability in caddyserver caddy prior to version 2.11.4. The issue arises because the forward_auth copy_headers feature deletes client-supplied identity headers but does not account for underscore aliases that survive deletion and later normalize into the same PHP/FastCGI variables. This allows remote clients to inject or override trusted identity or group headers in PHP/FastCGI applications behind Caddy. The vulnerability is fixed in version 2.11.4.
AI Analysis
Technical Summary
CVE-2026-52845 affects caddyserver caddy versions before 2.11.4. The forward_auth copy_headers mechanism deletes the exact client-supplied identity header before copying trusted values from the authentication gateway. However, HTTP headers are normalized by replacing dashes with underscores when passed to PHP/FastCGI, allowing a client to send an underscore alias header that bypasses the deletion step. This results in the ability for a remote attacker to inject or override identity or group headers trusted by PHP/FastCGI applications behind Caddy, leading to improper authentication. The vulnerability is addressed and fixed in caddy version 2.11.4.
Potential Impact
An attacker with network access can remotely inject or override identity and group headers that PHP/FastCGI applications behind Caddy trust for authentication and authorization decisions. This can lead to unauthorized access or privilege escalation within affected applications. The CVSS 3.1 score is 8.1 (High), reflecting high confidentiality and integrity impact with no impact on availability.
Mitigation Recommendations
This vulnerability is fixed in caddyserver caddy version 2.11.4. Users should upgrade to version 2.11.4 or later to remediate this issue. No official patch or temporary workaround is indicated beyond upgrading. Patch status is not explicitly confirmed in the vendor advisory excerpt, but the description states the issue is fixed in 2.11.4, indicating an official fix is available.
CVE-2026-52845: CWE-287: Improper Authentication in caddyserver caddy
Description
CVE-2026-52845 is an improper authentication vulnerability in caddyserver caddy prior to version 2.11.4. The issue arises because the forward_auth copy_headers feature deletes client-supplied identity headers but does not account for underscore aliases that survive deletion and later normalize into the same PHP/FastCGI variables. This allows remote clients to inject or override trusted identity or group headers in PHP/FastCGI applications behind Caddy. The vulnerability is fixed in version 2.11.4.
CVSS v3.1
Score 8.1high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-52845 affects caddyserver caddy versions before 2.11.4. The forward_auth copy_headers mechanism deletes the exact client-supplied identity header before copying trusted values from the authentication gateway. However, HTTP headers are normalized by replacing dashes with underscores when passed to PHP/FastCGI, allowing a client to send an underscore alias header that bypasses the deletion step. This results in the ability for a remote attacker to inject or override identity or group headers trusted by PHP/FastCGI applications behind Caddy, leading to improper authentication. The vulnerability is addressed and fixed in caddy version 2.11.4.
Potential Impact
An attacker with network access can remotely inject or override identity and group headers that PHP/FastCGI applications behind Caddy trust for authentication and authorization decisions. This can lead to unauthorized access or privilege escalation within affected applications. The CVSS 3.1 score is 8.1 (High), reflecting high confidentiality and integrity impact with no impact on availability.
Mitigation Recommendations
This vulnerability is fixed in caddyserver caddy version 2.11.4. Users should upgrade to version 2.11.4 or later to remediate this issue. No official patch or temporary workaround is indicated beyond upgrading. Patch status is not explicitly confirmed in the vendor advisory excerpt, but the description states the issue is fixed in 2.11.4, indicating an official fix is available.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-08T18:41:27.724Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a3acbe4eed863c81e6c9a54
Added to database: 06/23/2026, 18:09:40 UTC
Last enriched: 06/23/2026, 18:24:21 UTC
Last updated: 06/23/2026, 18:29:09 UTC
Views: 2
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