CVE-2026-55491

MEDIUMPre-NVD 5.45.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 5.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (19th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
5.4EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.4Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
5.4MEDIUMmedium confidence
EG Risk
24
EG Risk 24/100

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 (value × EchelonGraph’s weight)
Severity54% × 45%
The EG Score, 5.4 of 10.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
19th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 20, 2026

Last Modified

September 16, 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 advisoryMentions a patch (unverified)

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 13× in last 7d / 54× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  2. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  3. 2026-10-12 15:55 UTCEG score recompute
  4. 2026-10-11 19:39 UTCEG score recompute
  5. 2026-10-11 16:54 UTCEG score recompute
  6. 2026-10-11 14:17 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  9. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  10. 2026-10-09 08:14 UTCEG score recompute
  11. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  12. 2026-10-08 05:11 UTCEG score recompute
  13. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  14. 2026-10-07 01:15 UTCEG score recompute
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  16. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  17. 2026-10-05 01:33 UTCEG score recompute
  18. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  19. 2026-10-04 03:05 UTCEG score recompute
  20. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  21. 2026-10-03 05:08 UTCEG score recompute
  22. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  23. 2026-10-02 06:48 UTCEG score recompute
  24. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  25. 2026-10-01 06:04 UTCEG score recompute
Show 72 more
  1. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  2. 2026-09-30 08:07 UTCEG score recompute
  3. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  4. 2026-09-28 23:24 UTCEG score recompute
  5. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  6. 2026-09-28 00:49 UTCEG score recompute
  7. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  8. 2026-09-27 02:52 UTCEG score recompute
  9. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  10. 2026-09-24 19:41 UTCEG score recompute
  11. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  12. 2026-09-23 21:40 UTCEG score recompute
  13. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  14. 2026-09-22 23:43 UTCEG score recompute
  15. 2026-09-22 01:30 UTCEG score recompute
  16. 2026-09-21 03:34 UTCEG score recompute
  17. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  18. 2026-09-20 05:36 UTCEG score recompute
  19. 2026-09-19 07:39 UTCEG score recompute
  20. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  21. 2026-09-18 09:41 UTCEG score recompute
  22. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  23. 2026-09-17 11:44 UTCEG score recompute
  24. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  25. 2026-09-16 10:46 UTCEG score recompute
  26. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  27. 2026-09-15 12:43 UTCEG score recompute
  28. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  29. 2026-09-14 14:41 UTCEG score recompute
  30. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  31. 2026-09-12 18:47 UTCEG score recompute
  32. 2026-09-11 20:50 UTCEG score recompute
  33. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  34. 2026-09-10 22:45 UTCEG score recompute
  35. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  36. 2026-09-09 01:59 UTCEG score recompute
  37. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  38. 2026-09-08 04:02 UTCEG score recompute
  39. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  40. 2026-09-07 06:05 UTCEG score recompute
  41. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  42. 2026-09-06 08:07 UTCEG score recompute
  43. 2026-09-05 10:08 UTCEG score recompute
  44. 2026-09-04 12:08 UTCEG score recompute
  45. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  46. 2026-09-02 16:05 UTCEG score recompute
  47. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  48. 2026-09-01 17:34 UTCEG score recompute
  49. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  50. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  51. 2026-08-30 21:20 UTCEG score recompute
  52. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  53. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  54. 2026-08-29 01:26 UTCEG score recompute
  55. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  56. 2026-08-28 02:15 UTCEG score recompute
  57. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  58. 2026-08-27 04:10 UTCEG score recompute
  59. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  60. 2026-08-26 06:12 UTCEG score recompute
  61. 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  62. 2026-08-25 08:14 UTCEG score recompute
  63. 2026-08-24 10:14 UTCEG score recompute
  64. 2026-08-23 12:16 UTCEG score recompute
  65. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  66. 2026-08-22 14:19 UTCEG score recompute
  67. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 6th percentile
  68. 2026-08-21 16:22 UTCEG score recompute
  69. 2026-08-21 16:05 UTCEG score recompute
  70. 2026-08-20 22:24 UTCEG score recompute
  71. 2026-08-20 21:42 UTCEG score recomputeFirst assessed: 5.4 MEDIUM
  72. 2026-08-20 21:41 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-55491?
CVE-2026-55491 is a medium-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-55491 published?
The CVE record for CVE-2026-55491 was published on August 20, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 16, 2026; the record at its source may have been updated since.
Is CVE-2026-55491 actively exploited?
CVE-2026-55491 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (19th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55491?
CVE-2026-55491 has a CVSS base score of 5.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55491?
A fix for CVE-2026-55491 is available: update to the fixed version the vendor names in its advisory.

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