CVE-2026-28735

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

Score 5.4 from GitHub Security Advisory published 2026-05-26. the CNA's CVSS baseline 5.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:github_m, epss, ghsa
Trending — 3 sources updated this week
5.4
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.4Exploit: 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 validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628

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
3.6%
KEV
Not listed

Published

May 26, 2026

Last Modified

May 26, 2026

Vendor Advisories for CVE-2026-28735(1)

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

Affected Packages

(2 across 1 ecosystem)
Go(2)
PackageVulnerable rangeFixed inDependents
github.com/mattermost/mattermost-plugin-github—1.0.1-0.20260318132218-6e6b740c4852—
github.com/mattermost/mattermost-server11.6.011.6.1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 15× 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 123 total refreshes for this CVE.

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

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-28735?
CVE-2026-28735 is a medium 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 validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain…
When was CVE-2026-28735 disclosed?
CVE-2026-28735 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-2026-28735 actively exploited?
CVE-2026-28735 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-28735?
CVE-2026-28735 has a CVSS v4.0 base score of 5.4 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-28735?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-28735, 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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