Vulnerability DatabaseCVE-2024-21498

CVE-2024-21498:
vulnerability analysis and mitigation

Overview

CVE-2024-21498 affects all versions of the github.com/greenpau/caddy-security package, which is a security plugin for the Caddy web server. The vulnerability was discovered and disclosed on September 18, 2023, by security researchers from Trail of Bits. This Server-side Request Forgery (SSRF) vulnerability is exploitable via X-Forwarded-Host header manipulation (Trail of Bits Blog, Snyk Advisory).

Technical details

The vulnerability exists due to the caddy-security plugin processing the X-Forwarded-Host header without proper validation. This can be demonstrated by injecting host override headers in requests. The CVSS v3.1 base score is 5.3 (Medium) with the following vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N. The vulnerability is tracked as CWE-918 (Server-Side Request Forgery) (Snyk Advisory).

Impact

When exploited, this vulnerability allows attackers to expose sensitive information, interact with internal services, or exploit other vulnerabilities within the network. The plugin generates QR codes based on this header, which extends the attack surface. The impact includes potential web cache poisoning, business logic flaws, and routing-based SSRF vulnerabilities (GitHub Issue, Trail of Bits Blog).

Mitigation and workarounds

The recommended mitigation is to avoid relying on the Host and X-Forwarded-Host headers in the caddy-security plugin logic. Instead, use the current domain manually specified in the configuration file to generate QR codes. Additional recommendations include using Burp Suite Professional with the Param Miner extension to identify hidden header processing and expanding documentation to increase awareness of HTTP Host header attacks (GitHub Issue).

Community reactions

The vulnerability was initially reported to the caddy-security plugin maintainers on August 7, 2023. On August 23, 2023, the maintainers confirmed that there were no near-term plans to act on the reported vulnerabilities. The issue was publicly disclosed on September 18, 2023, as part of a larger security audit that revealed multiple vulnerabilities in the plugin (Trail of Bits Blog).