---
id: CVE-2026-75628
title: >-
  Punk::OAuth2 versions before 0.03 for Perl allow an attacker-chosen off-site
  redirect after login because same_origin_path accepts a backslash or tab in
  the return parameter
summary: >-
  Punk::OAuth2 versions before 0.03 for Perl allow an attacker-chosen off-site
  redirect after login because same_origin_path accepts a backslash or tab in
  the return parameter.


  oauth2_login reads the return parameter from the initiation r…
severity: medium
cvss: 5.7
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N'
cvssSource: adp
cwe:
  - CWE-601
product: Punk-OAuth2
affected:
  - Punk-OAuth2 < 0.03
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-28T15:11:05.001417Z'
published: '2026-08-20'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T21:19:28.700Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-75628'
references:
  - url: 'https://metacpan.org/release/LNATION/Punk-OAuth2-0.03/changes'
  - url: >-
      https://metacpan.org/release/LNATION/Punk-OAuth2-0.02/source/include/pox/pox_util.h#L94
  - url: 'https://datatracker.ietf.org/doc/html/rfc9700#section-4.11.1'
  - url: 'https://url.spec.whatwg.org/#relative-slash-state'
  - url: 'https://url.spec.whatwg.org/#concept-basic-url-parser'
tags:
  - cve.org
epss: 0.00503
epssPercentile: 0.41754
ingestedAt: '2026-10-19T21:43:56.120Z'
---

## Overview

Punk::OAuth2 versions before 0.03 for Perl allow an attacker-chosen off-site redirect after login because same_origin_path accepts a backslash or tab in the return parameter.

oauth2_login reads the return parameter from the initiation request, runs same_origin_path over it, and stores the survivor in the session flow record as the post-login redirect target. That check rejects a value that does not begin with a slash, one with a slash as its second byte, and one containing CR or LF. A backslash and a tab pass. The URL Standard treats a backslash as equivalent to a slash for special schemes, so `/\evil.example` parses with the authority `evil.example`. It also strips ASCII tab before parsing, so a tab between two leading slashes leaves `//evil.example`.

A crafted link to the application's own login route lands the victim on the attacker's site after a genuine authentication. The redirect carries no authorization code or access token.

## Affected

- `Punk-OAuth2 < 0.03`

## Remediation

Upgrade to Punk-OAuth2 0.03 or later.

### Workarounds

For deployments that cannot upgrade to 0.03, strip the return query parameter from requests to the oauth2_login initiation route at the reverse proxy. Logins then use the configured redirect_ok destination.