IRONSMITHINTEL
CRITICALCVSS9.8
|
Actively Exploited
|CISA KEV|CVE-2021-26084|Auth: none — unauthenticated|Reboot: required|Manual only

Atlassian Confluence Server and Data Center Object-Graph Navigation Language (OGNL) Injection Vulnerability

Atlassian Confluence Server and Data Server contain an Object-Graph Navigation Language (OGNL) injection vulnerability that may allow an unauthenticated attacker to execute code.

Published Aug 30, 2021 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2021-11-17 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-917) (CWE-917) vulnerability in Atlassian Confluence Server and Data Center. In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an unauthenticated attacker to execute arbitrary code on a Confluence Server or Data Center instance. The affected versions are before version 6.13.23, from version 6.14.0 before 7.4.11, from version 7.5.0 before 7.11.6, and from version 7.12.0 before 7.12.5. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

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Phishing link

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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 < 6.13.23, 6.14.0 ≤ v < 7.4.11, 7.5.0 ≤ v < 7.11.6, 7.12.0 ≤ v < 7.12.5; confluence server: v < 6.13.23, 6.14.0 ≤ v < 7.4.11, 7.5.0 ≤ v < 7.11.6, 7.12.0 ≤ v < 7.12.5
Real-world incidentsWhat we've seen

Used in known ransomware campaigns. Threat-research write-up: http://packetstormsecurity.com/files/167449/Atlassian-Confluence-Namespace-OGNL-Injection.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-67940
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2021-26084
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26084
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