CVE-2026-43929 Details
Description
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.
A vulnerability in the ssrfcheck library, specifically in versions through 1.3.0, allows Server-Side Request Forgery (SSRF) attacks to bypass the library's protections. This occurs when private IP addresses are encoded as IPv4-mapped IPv6 addresses, a format that the library's regex is unable to match. As a result, applications using the isSSRFSafeURL() function to validate user-supplied URLs before making HTTP requests are left exposed to SSRF attacks, including potential theft of cloud metadata or access to internal services not exposed to the internet.
Users are advised to update to a version of ssrfcheck that includes the fix for this vulnerability. As of now, no patched version is available.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed May 12, 2026CISA-ADP
Assessed May 13, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/felippe-regazio/ssrfcheck/security/advisories/GHSA-j4rj-2jr5-m439 | CISA-ADP | AdvisoryExploitRemedyVendor |
| https://github.com/felippe-regazio/ssrfcheck/security/advisories/GHSA-j4rj-2jr5-m439 | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-184 | Incomplete List of Disallowed Inputs | [email protected] |
| CWE-918 | Server-Side Request Forgery (SSRF) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| ssrfcheck | All versions |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 13, 2026 | CVE Modified | CISA-ADP |
| May 12, 2026 | New CVE Received | [email protected] |