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Pocket ID: OAuth redirect_uri validation bypass via userinfo/host confusion

High severity GitHub Reviewed Published Mar 7, 2026 in pocket-id/pocket-id • Updated Mar 10, 2026

Package

gomod github.com/pocket-id/pocket-id/backend (Go)

Affected versions

< 0.0.0-20260228130835-3a339e33191c

Patched versions

0.0.0-20260228130835-3a339e33191c

Description

Impact

A flaw in callback URL validation allowed crafted redirect_uri values containing URL userinfo (@) to bypass legitimate callback pattern checks. If an attacker can trick a user into opening a malicious authorization link, the authorization code may be redirected to an attacker-controlled host.

Patches

Fixed in v2.3.1 (commit 3a339e33191c31b68bf57db907f800d9de5ffbc8).
The fix replaces delimiter-based callback matching with structured URL pattern matching and updates validation logic/tests.

Workarounds

  • Reject callback URLs containing userinfo (@) at reverse proxy / app policy level if feasible.

References

@stonith404 stonith404 published to pocket-id/pocket-id Mar 7, 2026
Published to the GitHub Advisory Database Mar 9, 2026
Reviewed Mar 9, 2026
Published by the National Vulnerability Database Mar 10, 2026
Last updated Mar 10, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(2nd percentile)

Weaknesses

URL Redirection to Untrusted Site ('Open Redirect')

The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. Learn more on MITRE.

CVE ID

CVE-2026-28512

GHSA ID

GHSA-9h33-g3ww-mqff

Source code

Credits

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