CVE-2026-4915

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2026-05-26. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: 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 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
19.8%
KEV
Not listed

Published

May 25, 2026

Last Modified

June 1, 2026

Advisory Details (1)

Auto-updated Jun 14, 2026
No patch confirmed yet.
generic

Security Updates

https://mattermost.com/security-updates

Vendor Advisories for CVE-2026-4915(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-server—11.6.1+incompatible—
github.com/mattermost/mattermost-server/v5———
github.com/mattermost/mattermost-server/v6———
github.com/mattermost/mattermost/server/v8—8.0.0-20260407102538-faa7d75b4ea0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 45× 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 110 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-4915?
CVE-2026-4915 is a medium vulnerability published on May 25, 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 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook…
When was CVE-2026-4915 disclosed?
CVE-2026-4915 was first published in the National Vulnerability Database on May 25, 2026, with the most recent update on June 1, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-4915 actively exploited?
CVE-2026-4915 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 19.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-4915?
CVE-2026-4915 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-4915?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-4915, 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

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-4915

Explore →

Is Your Infrastructure Affected by CVE-2026-4915?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs