# CVE-2026-43929: ssrfcheck: Server-Side Request Forgery (SSRF) and Incomplete List of Disallowed Inputs

> Attackers can bypass SSRF protections in ssrfcheck using IPv4-mapped IPv6 addresses to access internal resources or cloud metadata.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 May 2026
- **Updated:** 13 May 2026
- **Also known as:** GHSA-j4rj-2jr5-m439

## What is CVE-2026-43929?

CVE-2026-43929 is a high-severity server-side request forgery vulnerability in felippe-regazio ssrfcheck, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-184 (Incomplete List of Disallowed Inputs)

## Which versions are affected by CVE-2026-43929?

2 open source packages ship an affected version, including ssrfcheck.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ssrfcheck` | npm | All versions to 1.3.0 | None |
| `ssrfcheck` | npm | All versions to 1.3.0 | None |

## How do I fix CVE-2026-43929?

No fix has been published for CVE-2026-43929 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-43929 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43929 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43929 and fix it if it is affected.

What it is: CVE-2026-43929 is a high-severity server-side request forgery vulnerability in felippe-regazio ssrfcheck, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43929 exists.

Affected packages and fixed versions:
- ssrfcheck (npm): affected all versions up to 1.3.0; no fix listed
- ssrfcheck (npm): affected all versions up to 1.3.0; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43929/ (Markdown: https://insights.sbomify.com/CVE-2026-43929/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43929
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43929
- OSV: https://osv.dev/vulnerability/CVE-2026-43929

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43929/
Summaries are generated and may contain mistakes; the official description above is the record.