IRONSMITHINTEL
MEDIUMCVSS5.3
|
Actively Exploited
|CISA KEV|CVE-2021-26085|Auth: none — unauthenticated|Reboot: required|Manual only

Atlassian Confluence Server Pre-Authorization Arbitrary File Read Vulnerability

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.

Published Aug 3, 2021 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve partial data exposure. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2022-04-18 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-425) (CWE-425) vulnerability in 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. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

📧

Phishing link

→

🖼

Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security
●Running confluence data center: v < 7.4.10, 7.5.0 ≤ v < 7.12.3; confluence server: v < 7.4.10, 7.5.0 ≤ v < 7.12.3
Real-world incidentsWhat we've seen

Used in known ransomware campaigns. Threat-research write-up: http://packetstormsecurity.com/files/164401/Atlassian-Confluence-Server-7.5.1-Arbitrary-File-Read.html

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

CISA required action: Apply updates per vendor instructions.

References

    1
    Vendor advisory: https://jira.atlassian.com/browse/CONFSERVER-67893
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2021-26085
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26085
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2021-26085↗ NVD↗ Vendor Advisory