CVE-2021-26084

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

Description

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

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.

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

PublishedAug 30, 2021

Last modifiedJun 17, 2026

Added to KEVNov 3, 2021

Remediation dueNov 17, 2021

References

packetstormsecurity.com/files/167449/Atlassian-Confluence-Namespace-OGNL-Injection.htmlExploitThird Party Advisory
jira.atlassian.com/browse/CONFSERVER-67940Issue TrackingPatch
cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26084US Government Resource

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Risk assessment · Critical

Actively exploited and used by ransomware crews. Patch immediately.

Exploitation: Confirmed in the wild (CISA KEV)
Federal remediation deadline: Overdue by 1804 days
Ransomware: Used in known ransomware campaigns
CVSS: 9.8 CRITICAL
EPSS (30-day exploit probability): 100.0% · top 1% of all CVEs
Weakness: CWE-917
Attack vector: Network, remotely reachable
Preconditions: No privileges and no user interaction

Recommended actions

1.Apply updates per vendor instructions.
2.Treat as emergency change: patch or isolate internet-facing instances first.
3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
5.Verify offline/immutable backups and segment the affected systems. This flaw is used for ransomware initial access.

Assessment is derived automatically from the live signals above; verify against your own asset inventory.