CVE-2026-55491

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 94% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

BigBlueButton is an open-source virtual classroom. Prior to 3.0.29, BigBlueButton failed to escape meetingName in record-and-playback/screenshare/playback/index.html.erb when generating the screenshare playback format. A low-privileged user could store a crafted meeting name that embedded script content, and the script executed in another user's browser when that user replayed the recording. This issue is fixed in version 3.0.29.

CVSS v3
5.4
EG Score
5.4(medium)
EG Risk
24(Track)
EG Risk 24/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity54% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
6%
KEV
Not listed

Published

August 20, 2026

Last Modified

August 21, 2026

Advisory Details (3)

Auto-updated Aug 20, 2026
Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

v3.0.29

Patch available: bigbluebutton/bigbluebutton v3.0.29

https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.29
github_commit

commit a53f2b920223 (bigbluebutton/bigbluebutton)

Fix landed in bigbluebutton/bigbluebutton commit a53f2b920223 — awaiting tagged release

https://github.com/bigbluebutton/bigbluebutton/commit/a53f2b92022388bfa4109d3136d1f3a932404b1b
github Patch Available

Stored XSS in Screenshare Recording Playback via Unescaped Meeting Name · Advisory · bigbluebutton/bigbluebutton · GitHub

https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-57p5-c888-74f9

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 20× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 01:26 UTCEG score recompute
  3. 2026-08-28 21:41 UTCEPSS rescore
  4. 2026-08-28 02:15 UTCEG score recompute
  5. 2026-08-27 14:25 UTCEPSS rescore
  6. 2026-08-27 04:10 UTCEG score recompute
  7. 2026-08-26 14:46 UTCEPSS rescore
  8. 2026-08-26 06:12 UTCEG score recompute
  9. 2026-08-25 13:49 UTCEPSS rescore
  10. 2026-08-25 08:14 UTCEG score recompute
  11. 2026-08-24 10:14 UTCEG score recompute
  12. 2026-08-23 12:16 UTCEG score recompute
  13. 2026-08-23 00:19 UTCEPSS rescore
  14. 2026-08-22 14:19 UTCEG score recompute
  15. 2026-08-21 23:49 UTCEPSS rescore
  16. 2026-08-21 16:22 UTCEG score recompute
  17. 2026-08-21 16:05 UTCEG score recompute
  18. 2026-08-20 22:24 UTCEG score recompute
  19. 2026-08-20 21:42 UTCEG score recompute
  20. 2026-08-20 21:41 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-55491?
CVE-2026-55491 is a medium vulnerability published on August 20, 2026. BigBlueButton is an open-source virtual classroom. Prior to 3.0.29, BigBlueButton failed to escape meetingName in record-and-playback/screenshare/playback/index.html.erb when generating the screenshare playback format. A low-privileged user could store a crafted meeting name that embedded script…
When was CVE-2026-55491 disclosed?
CVE-2026-55491 was first published in the National Vulnerability Database on August 20, 2026, with the most recent update on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55491 actively exploited?
CVE-2026-55491 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 94.0% of all scored CVEs.
What is the CVSS score of CVE-2026-55491?
CVE-2026-55491 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-55491?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55491, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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