Vulnerability · Published Sep 24, 2026 · Assigned by GitHub_M

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

High 8.5

In plain English

A high-severity server-side request forgery in logto from logto-io. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 4.0)8.5High

Exploit odds (30 days)0.3%top 77.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
logto-io	logto	< 1.43.0

Weakness: CWE-918 · 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

References

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