CVE-2026-46404 in BigBlueButton
Summary
by MITRE • 07/16/2026
BigBlueButton is an open-source virtual classroom. Prior to 3.0.23, the presentation URL validation did not properly restrict access to site local and link local addresses. The redirect following logic now pins resolved IPs. This issue is fixed in version 3.0.23.
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Analysis
by VulDB Data Team • 07/16/2026
The vulnerability in BigBlueButton versions prior to 3.0.23 represents a critical access control flaw that could enable unauthorized local network enumeration and potential lateral movement within organizational networks. This issue specifically affects the presentation URL validation mechanism, which failed to properly restrict access to site-local and link-local addresses that are typically restricted for security purposes. The flaw allows attackers to bypass intended network boundaries by exploiting improper URL handling during redirect operations.
The technical implementation of this vulnerability stems from insufficient input validation in the URL parsing and redirection logic. When processing presentation URLs, the system did not adequately sanitize or validate the target addresses before following redirects, permitting access to locally scoped IP addresses such as those in the 10.x.x.x, 172.16.x.x through 172.31.x.x, and 192.168.x.x ranges along with link-local addresses like 169.254.x.x. This improper validation creates a pathway for attackers to discover internal network topology and potentially access sensitive systems that should remain isolated from external exposure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can facilitate more sophisticated attacks including internal network reconnaissance, service enumeration, and potential privilege escalation within the local network environment. Attackers could leverage this flaw to map internal network structures, identify running services on internal hosts, and potentially exploit other vulnerabilities in systems that are normally protected by network segmentation policies. The redirect following logic that was subsequently patched demonstrates a classic case of insufficient IP address validation where resolved addresses were not properly pinned or restricted.
This vulnerability aligns with CWE-20, "Improper Input Validation," and specifically relates to improper restriction of URLs for redirects and forwards within the application's security model. The issue also maps to ATT&CK technique T1046, "Network Service Scanning,' as it enables attackers to enumerate services on internal network segments. Additionally, it corresponds to T1562.007, 'Taint/Corrupt Libraries,' when considering the potential for exploitation of the redirect mechanism in combination with other attack vectors.
The fix implemented in version 3.0.23 addresses this by modifying the redirect following logic to properly pin resolved IP addresses and implement stricter validation of target URLs. This change ensures that site-local and link-local addresses are appropriately restricted, preventing unauthorized access to internal network resources while maintaining legitimate functionality for external presentations and content delivery.
Organizations using BigBlueButton should immediately upgrade to version 3.0.23 or later to remediate this vulnerability. Security teams should also implement network monitoring to detect unusual redirect patterns or attempts to access local network addresses, as the vulnerability may be exploited in conjunction with other attack vectors. Regular security assessments of web application input validation mechanisms and network segmentation policies are recommended to prevent similar issues from arising in other components of the system architecture.