CVE-2026-48611 — PHPBB
CVE-2026-48611 is a Improper Authentication vulnerability in phpBB phpBB. Versions up to 3.3.16 are affected; the records list no fixed version yet, so check the vendor advisory below.
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.
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-48611.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Description
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.
Affected Products
phpBBphpBBDetection & mitigation playbook
Vendor / applianceDetect
Inventory every phpBB phpBB deployment and check each version against the affected-products list above.
Remediation status
The records we use list no fixed version for CVE-2026-48611 (versions up to 3.3.16 are affected). Check the phpBB phpBB advisory for a patched release, and apply the workarounds below until you can upgrade.
Mitigate without a patch
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2026-48611
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2026-48611 -u https://target- Template
- phpBB < 3.3.17 - Authentication Bypass
- Severity
- critical
- Impact
- An unauthenticated attacker can log in as any user including administrators, gaining full control over the phpBB forum, leading to data theft, defacement, and complete forum takeover.
- Remediation
- Upgrade phpBB to version 3.3.17 or later.
Template by ProjectDiscovery nuclei-templates (aikido, DhiyaneshDk), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2026-48611 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.