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Atomicorp WAF Research Note: CVE-2026-75628

Punk::OAuth2 versions before 0.03 for Perl allow an attacker-chosen off-site redirect after login because same_origin_pa

CVE Details

Status: Attack Blocked by Atomicorp
  • Already protected by existing Atomicorp WAF rules
  • Protection status: Understanding Atomicorp WAF Protection Status
  • CVE: CVE-2026-75628
  • Name: Punk::OAuth2 versions before 0.03 for Perl allow an attacker-chosen off-site redirect after login because same_origin_pa
  • Severity: Medium
  • CVSS: 5.7 (v3.1) (Medium)
  • CVSS version: 3.1
  • CVSS source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  • CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
    • Attack vector: Network
    • Attack complexity: Low
    • Privileges required: Low
    • User interaction: Required
    • Scope: Unchanged
    • Confidentiality impact: High
    • Integrity impact: None
    • Availability impact: None
  • CWE: CWE-601 — URL Redirection to Untrusted Site (‘Open Redirect’)
  • Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-178
  • Vendor: N/A
  • Vulnerable product: N/A
  • CVE published: 2026-08-20
  • CVE last modified: 2026-08-28
  • EPSS: 0.0041; 34.3th percentile (FIRST )
  • Latest Update: 2026-09-06
  • Selected Rule IDs observed: 344365
  • Matching rules: 1; rules with blocking actions: 1
  • Would-block Rule IDs: 344365
  • Request surfaces inspected: JSON request data, Request URI, Request argument names, Request arguments, Request headers, SOAP request data

Vulnerability Description

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.

  1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (344365 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

  2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

    • Affected versions: Product versions earlier than 0.03.
    • Recommended upgrade: Upgrade Product to 0.03 or later.
    • CNA guidance source: CPANSec
    • Vendor recommendation: Upgrade to Punk-OAuth2 0.03 or later.
    • Vendor workaround: 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.

  3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

Test or Research Source

  • Source: Atomicorp AI Research Framework
  • Tags: cve, derived, redirect, waf-probe

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

  • Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
  • Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
  • Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
  • Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
  • Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ .