Vulnerability in ssrfcheck (CVE-2026-43929)
Summary
Vulnerability in ssrfcheck (CVE-2026-43929). Confidential information can be exposed externally. Exploitable via ssrfcheck.
Original description
The description as published by the source.
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:
// src/is-private-ip.js (lines ~40-60 of the published source)
function privIp6 (ip) {
return /^::$/.test(ip) ||
/^::1$/.test(ip) ||
/^::f{4}:([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$/.test(ip) ||
/^::f{4}:0.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$/.test(ip) ||
/^64:ff9b::([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$/.test(ip) ||
// ... more patterns, all expect dot-notation ...
}
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 using `url.hos…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-43929 has been found in ssrfcheck.
Attackers can target a specific entry point like ssrfcheck over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.2/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "ssrfcheck CVE-2026-43929" on the vendor's site.
CVE-2026-43929 (ssrfcheck) — CWE-184 / CVSS v3 8.2
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: ssrfcheck / url.hostname / net.BlockList
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-184) exists in ssrfcheck. Attackers reach the vulnerable code path via ssrfcheck without authentication.
Check the vendor advisory for the affected versions of ssrfcheck. Attack surface: ssrfcheck / url.hostname / net.BlockList.
Severity: High (CVSS 8.2/10). Confidential information can be exposed externally.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'ssrfcheck' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'ssrfcheck' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
ssrfcheckを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com