CVE-2025-12421

CRITICALNVD 9.99.9—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.9 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 76% 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, nvd
9.9
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.9Exploit: NoneExposed: 0

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

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).

CVSS v3
9.9
EG Score
9.9(medium)
EG Risk
45(Track)
EG Risk 45/100SSVC: 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
Severity99% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
23.9%
KEV
Not listed

Published

November 27, 2025

Last Modified

December 3, 2025

Advisory Details (1)

Auto-updated Jul 20, 2026
No patch confirmed yet.
generic

Security Updates

https://mattermost.com/security-updates

Affected Packages

(4 across 1 ecosystem)
Go(4)
PackageVulnerable rangeFixed inDependents
github.com/mattermost/mattermost-server———
github.com/mattermost/mattermost-server/v5———
github.com/mattermost/mattermost-server/v6———
github.com/mattermost/mattermost/server/v8—8.0.0-20251022210333-acda1fb5dd46—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 42× 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. 2026-07-23 02:48 UTCEG score recompute
  2. 2026-07-22 14:07 UTCEPSS rescore
  3. 2026-07-22 14:07 UTCEPSS rescore
  4. 2026-07-21 15:24 UTCEPSS rescore
  5. 2026-07-19 02:28 UTCEPSS rescore
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  24. 2026-07-06 16:26 UTCEPSS rescore
  25. 2026-07-06 09:11 UTCOSV refresh
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  1. 2026-07-06 02:22 UTCEPSS rescore
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  3. 2026-07-05 02:30 UTCEPSS rescore
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  5. 2026-07-01 15:06 UTCEPSS rescore
  6. 2026-06-30 23:21 UTCEPSS rescore
  7. 2026-06-29 14:06 UTCEPSS rescore
  8. 2026-06-28 14:07 UTCEPSS rescore
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  10. 2026-06-28 04:55 UTCEPSS rescore
  11. 2026-06-27 03:08 UTCEPSS rescore
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  13. 2026-06-25 13:49 UTCEPSS rescore
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  17. 2026-06-23 21:32 UTCEPSS rescore
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  20. 2026-06-21 14:56 UTCEPSS rescore
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  22. 2026-06-21 01:59 UTCEPSS rescore
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  24. 2026-06-19 19:25 UTCEPSS rescore
  25. 2026-06-19 19:25 UTCEPSS rescore
  26. 2026-06-18 17:52 UTCEPSS rescore
  27. 2026-06-18 17:52 UTCEPSS rescore
  28. 2026-06-17 21:05 UTCOSV refresh
  29. 2026-06-17 17:52 UTCEPSS rescore
  30. 2026-06-16 17:52 UTCEPSS rescore
  31. 2026-06-15 17:48 UTCEPSS rescore
  32. 2026-06-14 23:17 UTCEPSS rescore
  33. 2026-06-13 22:59 UTCEPSS rescore
  34. 2026-06-13 22:59 UTCEPSS rescore
  35. 2026-06-12 23:11 UTCEPSS rescore
  36. 2026-06-11 13:59 UTCEPSS rescore
  37. 2026-06-10 22:18 UTCEPSS rescore
  38. 2026-06-10 13:21 UTCEPSS rescore
  39. 2026-06-08 14:16 UTCEPSS rescore
  40. 2026-06-08 14:16 UTCEPSS rescore
  41. 2026-06-07 15:24 UTCEPSS rescore
  42. 2026-06-06 13:47 UTCEPSS rescore
  43. 2026-06-06 13:47 UTCEPSS rescore
  44. 2026-06-05 22:46 UTCEPSS rescore
  45. 2026-06-05 22:46 UTCEPSS rescore
  46. 2026-06-05 06:10 UTCEPSS rescore
  47. 2026-06-05 06:10 UTCEPSS rescore
  48. 2026-06-04 13:11 UTCEPSS rescore
  49. 2026-06-04 13:11 UTCEPSS rescore
  50. 2026-06-02 20:12 UTCEPSS rescore
  51. 2026-06-02 20:12 UTCEPSS rescore
  52. 2026-06-01 13:51 UTCEPSS rescore
  53. 2026-06-01 13:51 UTCEPSS rescore
  54. 2026-05-31 00:16 UTCEPSS rescore
  55. 2026-05-31 00:16 UTCEPSS rescore
  56. 2026-05-29 18:47 UTCEG score recompute
  57. 2026-05-29 13:44 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2025-12421?
CVE-2025-12421 is a critical vulnerability published on November 27, 2025. Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email…
When was CVE-2025-12421 disclosed?
CVE-2025-12421 was first published in the National Vulnerability Database on November 27, 2025, with the most recent update on December 3, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-12421 actively exploited?
CVE-2025-12421 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 23.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-12421?
CVE-2025-12421 has a CVSS v3 base score of 9.9 (NVD).
How do I remediate CVE-2025-12421?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-12421, 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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