How severe is CVE-2020-26030?

CVE-2020-26030 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-26030 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-26030?

CVE-2020-26030 affects Zammad. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-26030?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2020-26030 published?

CVE-2020-26030 was published on 2020-12-28 and last updated on 2026-06-17.

CVE-2020-26030

CVE-2020-26030 is a critical-severity vulnerability in Zammad with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-287.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 1% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Zammad
Published: 2020-12-28
Last modified: 2026-06-17

Description

An issue was discovered in Zammad before 3.4.1. There is an authentication bypass in the SSO endpoint via a crafted header, when SSO is not configured. An attacker can create a valid and authenticated session that can be used to perform any actions in the name of other users.

Frequently asked questions

What is CVE-2020-26030?: An issue was discovered in Zammad before 3.4.1. There is an authentication bypass in the SSO endpoint via a crafted header, when SSO is not configured. An attacker can create a valid and authenticated session that can be used to perform any actions in the name of other users.
How severe is CVE-2020-26030?: CVE-2020-26030 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-26030 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-26030?: CVE-2020-26030 affects Zammad. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-26030?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-26030 published?: CVE-2020-26030 was published on 2020-12-28 and last updated on 2026-06-17.

References

https://zammad.com/news/security-advisory-zaa-2020-18

Affected products (1)

cpe:2.3:a:zammad:zammad:*:*:*:*:*:*:*:*

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