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MEDIUM · CVSS 5.3 CISA Known Exploited Vulnerability

CVE-2021-26085

Atlassian Confluence Server Pre-Authorization Arbitrary File Read Vulnerability

Atlassian Confluence Server

Affected versions of Atlassian Confluence Server allow remote attackers to view restricted resources via a Pre-Authorization Arbitrary File Read vulnerability in the /s/ endpoint. The affected versions are before version 7.4.10, and from version 7.5.0 before 7.12.3.

CVSS
5.3
MEDIUM
EPSS
99.9%
30-day exploitation
Ransomware groups
0
recorded exploiting
Published
3 Aug 2021
CWE-425

Exploitation status

CISA Known Exploited Vulnerabilities

Listed by CISA on 28 March 2022. US federal agencies were required to remediate it by 18 April 2022. CISA records this vulnerability as known to be used in ransomware campaigns.

EPSS — exploitation probability

FIRST puts the probability of exploitation activity in the next 30 days at 99.9%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Frequently asked questions

Is CVE-2021-26085 being exploited by ransomware groups?

No ransomware group in this database is currently recorded as exploiting CVE-2021-26085.

What does CVE-2021-26085 affect?

CVE-2021-26085 affects Atlassian Confluence Server. Affected versions of Atlassian Confluence Server allow remote attackers to view restricted resources via a Pre-Authorization Arbitrary File Read vulnerability in the /s/ endpoint. The affected versions are before version 7.4.10, and from version 7.5.0 before 7.12.3.

How severe is CVE-2021-26085?

CVE-2021-26085 is rated MEDIUM with a CVSS base score of 5.3. EPSS puts the probability of exploitation in the next 30 days at 99.9%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 18 April 2022.

How should organisations respond to CVE-2021-26085?

Apply the vendor patch for Atlassian Confluence Server as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.