What is CVE-2026-48611?

CVE-2026-48611 is a critical-severity vulnerability in Phpbb, classified under Improper Authentication. CVSS score: 9.8/10. Published 2026-06-12.

How severe is CVE-2026-48611?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2026-48611 known to be exploited?

3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Auth bypass in Phpbb

CVE-2026-48611

Improper authentication checks in the OAuth implementation allow account hijacking even when OAuth is not configured or enabled leading to unauthorized access in default installations.

Vulnerability class: Broken Authentication

EPSS: 0.039 (89.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Phpbb — versions 3.3.0

Weakness classification (CWE)

CWE-287 — Improper Authentication

Public proof-of-concept exploits

References

support@hackerone.com

Frequently asked questions

What is CVE-2026-48611?: CVE-2026-48611 is a critical-severity vulnerability in Phpbb, classified under Improper Authentication. CVSS score: 9.8/10. Published 2026-06-12.
How severe is CVE-2026-48611?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-48611 known to be exploited?: 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.