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.
CVE-2026-84458
“—” beside the score: it is equal to the CVSS score beside it.
This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (29th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Also known asEUVD-2026-87261 (ENISA EUVD)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
The CVE record names the fixed release — apply it.
- CVSS v3
- 9.1
- EG Score
- 9.1CRITICALmedium confidence
- EG Risk
- 56EG Risk 56/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity91% × 45%Impact severity (EG Severity): CVSS 9.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.4% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability100% × 15%CISA's SSVC Automatable value: yes (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: The CVE record names the fixed release. 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
- 29th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.1): severity, escalated by confirmed exploitation. This CVE's 9.1 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.1 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
The CVE record names the fixed release. 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). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 60 days if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
September 25, 2026
Last Modified
September 28, 2026
Advisory Details (2)
Auto-updated Sep 25, 2026commit 0dba387df8e2 (zammad/zammad)
Fix landed in zammad/zammad commit 0dba387df8e2 — awaiting tagged release
https://github.com/zammad/zammad/commit/0dba387df8e2b46956907975034cd44e4d021b1cAccount takeover via unverified email matching during SSO auto-link · Advisory · zammad/zammad · GitHub
https://github.com/zammad/zammad/security/advisories/GHSA-86cc-3ggh-mf2mWeakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 13× in last 7d / 63× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
- 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
- 2026-11-01 11:05 UTCEG score recompute
- 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
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- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 28th percentile
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- 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 28th percentile
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- 2026-10-21 15:26 UTCEG score recompute
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- 2026-10-20 13:54 UTCEG score recompute
- 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.4% · 27th percentile
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- 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.4% · 27th percentile
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- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 27th percentile
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- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 27th percentile
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- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 27th percentile
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- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 26th percentile
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- 2026-09-30 15:04 UTCEPSS rescoreEPSS 0.4% · 26th percentile
- 2026-09-29 17:02 UTCEG score recompute
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- 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.4% · 26th percentile
- 2026-09-27 15:13 UTCEG score recompute
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 26th percentile
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- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 26th percentile
- 2026-09-25 19:34 UTCEG score recompute
- 2026-09-25 19:11 UTCEG score recompute
- 2026-09-25 18:32 UTCEG score recomputeFirst assessed: 9.1 CRITICAL
- 2026-09-25 18:30 UTCMITRE cvelistV5first tracked
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Frequently asked(5)
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Dependency Blast Radius
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