CVE-2021-26084
RCE in Atlassian Confluence Data Center ≤ 6.13.23
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2021-26084 is a critical-severity Expression Language Injection (CWE-917) vulnerability in Atlassian Confluence Data Center. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2021-26084 is an OGNL injection vulnerability affecting Confluence Server and Data Center. The flaw exists in versions before 6.13.23, from 6.14.0 before 7.4.11, from 7.5.0 before 7.11.6, and from 7.12.0 before 7.12.5, and is tracked under CWE-917. It carries a CVSS 3.1 score of 9.8 reflecting network-accessible exploitation with no required credentials or user interaction.
An unauthenticated remote attacker can supply malicious OGNL expressions to the affected instance and achieve arbitrary code execution on the underlying server, resulting in full confidentiality, integrity, and availability impact.
Atlassian’s Jira entry CONFSERVER-67940 and associated security advisory provide patch details and upgrade guidance to the fixed releases listed above. The vulnerability appears in CISA’s catalog of known exploited vulnerabilities, and public exploit code has been published on PacketStorm.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-12905
Vulnerability Data
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…
more
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.
- CWE(s)
- KEV Date Added
- 03 November 2021
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.1.2V1.3.2V1.3.5V4.3.1
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require input neutralization and safe EL construction to prevent injection flaws.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance can detect EL injection but does not itself implement the fix.
Secure SDLC mandates input validation and output encoding that directly prevent expression-language injection.
Application security requirements explicitly call for controls against injection flaws including EL injection.
Secure architecture principles reduce the attack surface but do not prescribe the specific neutralization techniques needed.
Secure coding standards require proper escaping and parameterization of expression-language statements.