CVE-2021-26085 — Confluence Data Center
MEDIUMCVE-2021-26085 is a medium-severity (CVSS 5.3) CWE-425 vulnerability in atlassian confluence data center. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-03-28) and has been used in ransomware campaigns — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
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…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-03-28 — including use in ransomware campaigns. Federal agencies were required to remediate by 2022-04-18.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-26085.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-26085 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.
Description
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.
Affected Products
confluence data centeratlassianconfluence serveratlassianResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Atlassian Confluence 7.12.2 - Pre-Authorization Arbitrary File Read
by Mayank Deshmukh · Oct 5, 2021
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every atlassian confluence data center deployment and check each version against the affected-products list above.
Fix
Apply the atlassian confluence data center security patch or hotfix for CVE-2021-26085 on the affected version, following the vendor advisory for your exact build.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2021-26085
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2021-26085 -u https://target- Template
- Atlassian Confluence Server - Local File Inclusion
- Severity
- medium
- Impact
- An attacker can access sensitive information stored on the server, potentially leading to unauthorized access or data leakage.
- Remediation
- Apply the latest security patches provided by Atlassian to fix the vulnerability.
Template by ProjectDiscovery nuclei-templates (princechaddha), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2021-26085 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.