ssrfcheck Vulnerable to Server-Side Request Forgery (SSRF) and Incomplete List of Disallowed Inputs

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS

• CVE-2026-43929: 0.27% estimated exploitation activity in the next 30 days; percentile 19.15 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary ssrfcheck v1.3.0 (latest) 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. --- Details Vulnerable file: src/is-private-ip.js The library detects IPv6 private addresses using the privIp6() function. The relevant portion: The third line is the IPv4-mapped IPv6 check. It expects input in the form ::ffff:127.0.0.1 (dots). However, the IP is extracted from the URL…

Published by the source

5 May 2026, 20:29 UTC

Last modified by the source

13 May 2026, 16:35 UTC

Source last checked

26 Oct 2026, 12:52 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j4rj-2jr5-m439

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-j4rj-2jr5-m439

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# Patch Next advisory brief: CVE-2026-43929

Advisory: ssrfcheck Vulnerable to Server-Side Request Forgery (SSRF) and Incomplete List of Disallowed Inputs
IDs: CVE-2026-43929, GHSA-j4rj-2jr5-m439
Record: https://patchnext.com/advisories/cve-2026-43929 (revision 2, source checked 26 Oct 2026, 12:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm ssrfcheck: affected <= 1.3.0

## Suggested inspection (read-only)
- `npm ls ssrfcheck --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ssrfcheck.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-j4rj-2jr5-m439 (OSV record GHSA-j4rj-2jr5-m439 lists affected ranges: npm ssrfcheck >=0 <=1.3.0)
- Verified: https://github.com/advisories/GHSA-j4rj-2jr5-m439 (GitHub-reviewed advisory GHSA-j4rj-2jr5-m439 lists affected ranges: npm ssrfcheck >=0 <=1.3.0)

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