CVE-2026-43929
HighCVSS 8.2Exploitation Probability (EPSS)
Low risk19th percentile - higher than 19% of all known CVEs
Summary
The ssrfcheck library in versions 1.3.0 and earlier fails to block Server-Side Request Forgery (SSRF) attacks when the target private IP address is encoded as an IPv4-mapped IPv6 address. The URL parser built into Node.js normalizes the IPv4 notation, causing the regex to miss the threat.
Risk Assessment
Organizations using this library are exposed to SSRF attacks, which may lead to unauthorized access to internal resources and data leakage.
Recommendation
It is recommended to update the ssrfcheck library to the latest version that fixes this vulnerability and to review applications using the isSSRFSafeURL() function for additional protection.
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Original NVD description (English source)
ssrfcheck is a library that checks if a string contains a potential SSRF attack. In 1.3.0 and earlier, ssrfcheck fails to block Server-Side Request Forgery attacks when the target private IP address is encoded as an IPv4-mapped IPv6 address (e.g. http://[::ffff:127.0.0.1]/). The WHATWG URL parser built into Node.js silently normalizes the IPv4 notation inside the brackets to compressed hex form ([::ffff:7f00:1]) before the library's private-IP regex ever runs. The regex was written to match dot-notation only and therefore never matches any real input — all seven IANA private IPv4 ranges, including the AWS/GCP/Azure metadata address 169.254.169.254, are bypassed. Any application using isSSRFSafeURL() to guard HTTP requests made with user-supplied URLs is fully exposed to SSRF.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS