Cyber Resilience

CVE-2026-27736

Open Redirect in Bigbluebutton ≤ 3.0.20

Open Redirect
Published
25 February 2026
Modified
05 March 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.1
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS Score 0.0015 4th percentile
Risk Priority 44 floored blend · peak EPSS

Summary

CVE-2026-27736 is a medium-severity Open Redirect (CWE-601) vulnerability in Bigbluebutton Bigbluebutton. Its CVSS base score is 6.1 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Phishing (T1566); ranked at the 4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability Data

BigBlueButton is an open-source virtual classroom. In versions on the 3.x branch prior to 3.0.20, the string received with errorRedirectUrl lacks validation, using it directly in the respondWithRedirect function leads to an Open Redirect vulnerability. BigBlueButton 3.0.20 patches the issue.…

more

No known workarounds are available.

CWE(s)
CWE-601

Related Threats

MITRE ATT&CK Enterprise Techniques

T1566 Phishing Initial Access
Adversaries may send phishing messages to gain access to victim systems.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-27467Same product: Bigbluebutton Bigbluebutton
CVE-2025-61601Same product: Bigbluebutton Bigbluebutton
CVE-2023-42803Same product: Bigbluebutton Bigbluebutton
CVE-2023-43797Same product: Bigbluebutton Bigbluebutton
CVE-2025-55200Same product: Bigbluebutton Bigbluebutton
CVE-2023-42804Same product: Bigbluebutton Bigbluebutton
CVE-2025-61602Same product: Bigbluebutton Bigbluebutton
CVE-2026-27466Same product: Bigbluebutton Bigbluebutton
CVE-2023-33176Same product: Bigbluebutton Bigbluebutton
CVE-2023-43798Same product: Bigbluebutton Bigbluebutton

Affected Assets

bigbluebutton
bigbluebutton
≤ 3.0.20

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V3.7.2

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

Input validation directly checks and rejects untrusted redirect targets before they are used in a response.

AC-4 Information Flow Enforcement partial match

Information flow enforcement can restrict redirects to only approved/trusted destinations, stopping untrusted user-supplied URLs from being followed.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and untrusted-redirect controls that prevent CWE-601.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.23 Web filtering partial match
mitigates

Preventing access to attacker-controlled or malicious sites stops users from being redirected to untrusted locations via open-redirect or phishing links.

References