What’s Vulnerable › Vulnerabilities

CVE-2020-12443

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-04-29 · updated 2026-06-17
• Weakness: CWE-22

Description

BigBlueButton before 2.2.6 allows remote attackers to read arbitrary files because the presfilename (lowercase) value can be a .pdf filename while the presFilename (mixed case) value has a ../ sequence. This can be leveraged for privilege escalation via a directory traversal to bigbluebutton.properties. NOTE: this issue exists because of an ineffective mitigation to CVE-2020-12112 in which there was an attempted fix within an NGINX configuration file, without considering that the relevant part of NGINX is case-insensitive.

Affected products

• bigbluebutton: before 2.2.6 — fixed in 2.2.6

How to fix

Upgrade to a fixed version: bigbluebutton 2.2.6. Check the vendor advisory for mitigations.

References

• https://github.com/bigbluebutton/bigbluebutton/pull/9259/commits/b21ca8355a57286a1e6df96984b3a4c57679a463
• https://github.com/mclab-hbrs/BBB-POC
• https://github.com/bigbluebutton/bigbluebutton/pull/9259/commits/b21ca8355a57286a1e6df96984b3a4c57679a463
• https://github.com/mclab-hbrs/BBB-POC

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