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

> Administrators can trigger Server-Side Request Forgery via webhooks or OAuth connectors, potentially exposing internal data or credentials.

- **Severity:** High 8.5 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** GHSA-3556-624q-c5w3

## What is CVE-2026-56739?

CVE-2026-56739 is a high-severity server-side request forgery vulnerability in logto-io logto, published on 24 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-56739?


## How do I fix CVE-2026-56739?

No fix has been published for CVE-2026-56739 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-56739 being exploited?

There is no known exploitation of CVE-2026-56739 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56739 and fix it if it is affected.

What it is: CVE-2026-56739 is a high-severity server-side request forgery vulnerability in logto-io logto, published on 24 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-56739 in the wild and no public exploit code.

Affected product: logto-io logto. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-56739/ (Markdown: https://insights.sbomify.com/CVE-2026-56739/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56739
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56739
- OSV: https://osv.dev/vulnerability/CVE-2026-56739

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56739/
Summaries are generated and may contain mistakes; the official description above is the record.