CVE-2026-84458

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (27th percentile of EPSS-scored CVEs). 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, secondary
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when the "Automatic account link on initial logon" setting is enabled, Zammad binds an incoming third-party (SSO) identity to an existing local account by matching the email address the identity provider reports, without verifying that the provider actually confirmed ownership of that email. An attacker who controls any identity at a configured provider, including, by default, any Azure AD tenant via Zammad's multi-tenant Microsoft 365 /common app registration, can set that identity's email to a victim's address, authenticate, and be logged in as the victim. This bypasses the victim's local password entirely and affects any existing account, including agents and administrators. Zammad will honor the xms_edov ID token claim when email verification is required in the Microsoft 365 setting, treating a missing claim as unverified. This issue is fixed in version 7.1.2.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
56
EG Risk 56/100CISA SSVC

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
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
27th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 25, 2026

Last Modified

September 28, 2026

Advisory Details (2)

Auto-updated Sep 25, 2026
Patch available. Sources: github, github_commit.
github_commit

commit 0dba387df8e2 (zammad/zammad)

Fix landed in zammad/zammad commit 0dba387df8e2 — awaiting tagged release

https://github.com/zammad/zammad/commit/0dba387df8e2b46956907975034cd44e4d021b1c
github Patch Available

Account takeover via unverified email matching during SSO auto-link · Advisory · zammad/zammad · GitHub

https://github.com/zammad/zammad/security/advisories/GHSA-86cc-3ggh-mf2m

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 20× 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. 2026-10-03 15:27 UTCEG score recompute
  2. 2026-10-03 14:26 UTCEPSS rescore
  3. 2026-10-02 21:57 UTCEG score recompute
  4. 2026-10-02 17:57 UTCEPSS rescore
  5. 2026-10-02 00:03 UTCEG score recompute
  6. 2026-10-01 19:50 UTCEPSS rescore
  7. 2026-09-30 17:24 UTCEG score recompute
  8. 2026-09-30 15:04 UTCEPSS rescore
  9. 2026-09-29 17:02 UTCEG score recompute
  10. 2026-09-28 23:35 UTCEG score recompute
  11. 2026-09-28 14:51 UTCEG score recompute
  12. 2026-09-28 13:52 UTCEPSS rescore
  13. 2026-09-27 15:13 UTCEG score recompute
  14. 2026-09-27 13:48 UTCEPSS rescore
  15. 2026-09-26 17:21 UTCEG score recompute
  16. 2026-09-26 15:59 UTCEPSS rescore
  17. 2026-09-25 19:34 UTCEG score recompute
  18. 2026-09-25 19:11 UTCEG score recompute
  19. 2026-09-25 18:32 UTCEG score recompute
  20. 2026-09-25 18:30 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-84458?
CVE-2026-84458 is a critical vulnerability published on September 25, 2026. Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when the "Automatic account link on initial logon" setting is enabled, Zammad binds an incoming third-party (SSO) identity to an existing local account by matching the email address the identity provider reports,…
When was CVE-2026-84458 disclosed?
CVE-2026-84458 was first published on September 25, 2026, with the most recent update on September 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-84458 actively exploited?
CVE-2026-84458 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (27th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-84458?
CVE-2026-84458 has a CVSS base score of 9.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-84458?
A fix for CVE-2026-84458 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-84458

Explore →

Is Your Infrastructure Affected by CVE-2026-84458?

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

Book a Demo →Browse All CVEs