CVE-2026-5740

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-05-26. the CNA's CVSS baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:github_m, epss, ghsa
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

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

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14...

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an unauthenticated remote attacker to crash the server process and cause a full service outage for all users via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID: MMSA-2026-00647

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
—
EPSS
25.1%
KEV
Not listed

Published

May 26, 2026

Last Modified

May 26, 2026

Vendor Advisories for CVE-2026-5740(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(4 across 1 ecosystem)
Go(4)
PackageVulnerable rangeFixed inDependents
github.com/mattermost/mattermost-server11.6.011.6.1—
github.com/mattermost/mattermost-server/v5———
github.com/mattermost/mattermost-server/v6———
github.com/mattermost/mattermost/server/v8—8.0.0-20260410202636-17939826efa2—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 51× 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.

Showing the most recent 100 of 131 total refreshes for this CVE.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-22 14:08 UTCEPSS rescore
  3. 2026-07-21 15:25 UTCEPSS rescore
  4. 2026-07-21 15:25 UTCEPSS rescore
  5. 2026-07-20 17:08 UTCEPSS rescore
  6. 2026-07-19 14:31 UTCEPSS rescore
  7. 2026-07-19 08:22 UTCOSV refresh
  8. 2026-07-19 02:29 UTCEPSS rescore
  9. 2026-07-18 10:04 UTCEPSS rescore
  10. 2026-07-16 17:03 UTCEPSS rescore
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-15 02:00 UTCEPSS rescore
  13. 2026-07-15 02:00 UTCEPSS rescore
  14. 2026-07-13 22:31 UTCEPSS rescore
  15. 2026-07-13 06:13 UTCEPSS rescore
  16. 2026-07-13 06:13 UTCEPSS rescore
  17. 2026-07-12 05:46 UTCEPSS rescore
  18. 2026-07-11 08:27 UTCEPSS rescore
  19. 2026-07-11 08:27 UTCEPSS rescore
  20. 2026-07-09 19:10 UTCEPSS rescore
  21. 2026-07-09 19:10 UTCEPSS rescore
  22. 2026-07-08 15:16 UTCEPSS rescore
  23. 2026-07-08 15:16 UTCEPSS rescore
  24. 2026-07-07 13:46 UTCEPSS rescore
  25. 2026-07-07 13:46 UTCEPSS rescore
Show 75 more
  1. 2026-07-06 16:27 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 02:23 UTCEPSS rescore
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-05 02:31 UTCEPSS rescore
  6. 2026-07-05 02:30 UTCEPSS rescore
  7. 2026-07-04 06:31 UTCEPSS rescore
  8. 2026-07-04 06:31 UTCEPSS rescore
  9. 2026-07-01 15:07 UTCEPSS rescore
  10. 2026-06-30 23:22 UTCEPSS rescore
  11. 2026-06-29 15:52 UTCGHSA enrichment
  12. 2026-06-29 14:06 UTCEPSS rescore
  13. 2026-06-29 01:06 UTCGHSA enrichment
  14. 2026-06-28 14:07 UTCEPSS rescore
  15. 2026-06-28 07:37 UTCGHSA enrichment
  16. 2026-06-28 04:56 UTCEPSS rescore
  17. 2026-06-27 19:01 UTCGHSA enrichment
  18. 2026-06-27 07:08 UTCGHSA enrichment
  19. 2026-06-27 03:08 UTCEPSS rescore
  20. 2026-06-26 18:47 UTCGHSA enrichment
  21. 2026-06-25 23:50 UTCGHSA enrichment
  22. 2026-06-25 13:50 UTCEPSS rescore
  23. 2026-06-25 12:29 UTCGHSA enrichment
  24. 2026-06-24 14:05 UTCEPSS rescore
  25. 2026-06-23 21:33 UTCEPSS rescore
  26. 2026-06-23 21:33 UTCEPSS rescore
  27. 2026-06-22 14:25 UTCEPSS rescore
  28. 2026-06-22 14:25 UTCEPSS rescore
  29. 2026-06-21 14:56 UTCEPSS rescore
  30. 2026-06-21 14:56 UTCEPSS rescore
  31. 2026-06-21 01:59 UTCEPSS rescore
  32. 2026-06-21 01:59 UTCEPSS rescore
  33. 2026-06-19 19:26 UTCEPSS rescore
  34. 2026-06-19 19:26 UTCEPSS rescore
  35. 2026-06-18 17:52 UTCEPSS rescore
  36. 2026-06-18 17:52 UTCEPSS rescore
  37. 2026-06-17 19:24 UTCGHSA enrichment
  38. 2026-06-17 17:53 UTCEPSS rescore
  39. 2026-06-17 04:56 UTCGHSA enrichment
  40. 2026-06-16 17:53 UTCEPSS rescore
  41. 2026-06-16 17:27 UTCGHSA enrichment
  42. 2026-06-16 01:32 UTCGHSA enrichment
  43. 2026-06-15 17:49 UTCEPSS rescore
  44. 2026-06-15 17:49 UTCEPSS rescore
  45. 2026-06-15 13:56 UTCGHSA enrichment
  46. 2026-06-15 00:28 UTCGHSA enrichment
  47. 2026-06-14 23:18 UTCEPSS rescore
  48. 2026-06-14 13:06 UTCGHSA enrichment
  49. 2026-06-14 01:44 UTCGHSA enrichment
  50. 2026-06-13 23:00 UTCEPSS rescore
  51. 2026-06-13 14:17 UTCGHSA enrichment
  52. 2026-06-13 02:55 UTCGHSA enrichment
  53. 2026-06-12 23:12 UTCEPSS rescore
  54. 2026-06-12 23:12 UTCEPSS rescore
  55. 2026-06-12 15:34 UTCGHSA enrichment
  56. 2026-06-12 04:01 UTCGHSA enrichment
  57. 2026-06-11 16:40 UTCGHSA enrichment
  58. 2026-06-11 14:00 UTCEPSS rescore
  59. 2026-06-11 03:57 UTCGHSA enrichment
  60. 2026-06-10 22:19 UTCEPSS rescore
  61. 2026-06-10 16:36 UTCGHSA enrichment
  62. 2026-06-10 13:22 UTCEPSS rescore
  63. 2026-06-10 05:14 UTCGHSA enrichment
  64. 2026-06-09 17:52 UTCGHSA enrichment
  65. 2026-06-09 06:31 UTCGHSA enrichment
  66. 2026-06-08 19:09 UTCGHSA enrichment
  67. 2026-06-08 14:17 UTCEPSS rescore
  68. 2026-06-08 04:37 UTCGHSA enrichment
  69. 2026-06-07 17:16 UTCGHSA enrichment
  70. 2026-06-07 15:25 UTCEPSS rescore
  71. 2026-06-07 05:55 UTCGHSA enrichment
  72. 2026-06-06 18:33 UTCGHSA enrichment
  73. 2026-06-06 13:47 UTCEPSS rescore
  74. 2026-06-06 07:11 UTCGHSA enrichment
  75. 2026-06-05 22:47 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-5740?
CVE-2026-5740 is a high vulnerability published on May 26, 2026. Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14... Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to properly validate msgpack-encoded WebSocket frames before memory allocation which allows an…
When was CVE-2026-5740 disclosed?
CVE-2026-5740 was first published in the National Vulnerability Database on May 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-5740 actively exploited?
CVE-2026-5740 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 25.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-5740?
CVE-2026-5740 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-5740?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-5740, 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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