CVE-2019-25211: 
Linux Debian vulnerability analysis and mitigation

CVE-2019-25211 affects the parseWildcardRules function in Gin-Gonic CORS middleware before version 1.6.0. The vulnerability involves mishandling of wildcard characters at the end of origin strings, where patterns like https://example.com/ would incorrectly match unintended domains like https://example.community/ (NVD).

The vulnerability exists in the parseWildcardRules function where if a wildcard is at the end of the origin string, the character right before the wildcard is incorrectly cut off. This occurs due to a bug in the substring operation where o[:i-1] is used instead of o[:i] when processing the wildcard at the end of the string. This implementation error leads to broader pattern matching than intended (GitHub PR).

The vulnerability can lead to security bypass where malicious domains could be incorrectly validated as allowed origins. For example, when configuring https://example.* as an allowed origin, the middleware would incorrectly match unauthorized domains like https://example-without-a-dot.com or https://example.attacker.com (GitHub PR).

The issue has been fixed in version 1.6.0 of the Gin-Gonic CORS middleware. Users should upgrade to this version or later to receive the fix. The fix corrects the substring operation to properly handle wildcards at the end of origin strings (GitHub Release).