CVE-2021-26084: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-855c-xp53-5fp2
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CVSS 9.8
CWE-917 CWE-74
Published
Advisory Summary

CVE-2021-26084 is a CRITICAL (CVSS 9.8) security vulnerability vulnerability (CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product constructs all or part of an expression language (el) statement in a framework such as a java server page (jsp) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended el statement before it is executed.. Remediation is available in the latest vendor maintenance releases.

CVE-2021-26084 at a Glance

CVE Identifier CVE-2021-26084
GHSA Identifier GHSA-855c-xp53-5fp2
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-26084

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-26084, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection'), where the product constructs all or part of an expression language (el) statement in a framework such as a java server page (jsp) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended el statement before it is executed. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an authenticated user, and in some instances an unauthenticated user, to execute arbitrary code on a Confluence Server or Data Center instance. The vulnerable endpoints can be accessed by a non-administrator user or unauthenticated user if ‘Allow people to sign up to create their account’ is enabled. To check whether this is enabled go to COG > User Management > User Signup Options. 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.

References

NVD — CVE-2021-26084 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-26084
jira.atlassian.com/browse/confserver-6... WEB
https://jira.atlassian.com/browse/CONFSERVER-67940
www.cisa.gov/known-exploited-vul... WEB
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26084
Software Security Information SECURITY
http://packetstormsecurity.com/files/164013/Confluence-Server-7.12.4-OGNL-Injection-Remote-Code-Execution.html
Software Security Information SECURITY
http://packetstormsecurity.com/files/164122/Atlassian-Confluence-WebWork-OGNL-Injection.html
Software Security Information SECURITY
http://packetstormsecurity.com/files/167449/Atlassian-Confluence-Namespace-OGNL-Injection.html

Frequently Asked Questions

What is CVE-2021-26084?
CVE-2021-26084 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection').
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2021-26084?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2021-26084?
CVE-2021-26084 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-26084?
CVE-2021-26084 is classified under CWE-917: Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') (The product constructs all or part of an expression language (EL) statement in a framework such as a Java Server Page (JSP) using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended EL statement before it is executed.).
How can I check Maven dependencies for CVE-2021-26084?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-855c-xp53-5fp2",
  "modified" : "2025-10-22T00:32:19Z",
  "published" : "2022-05-24T22:28:25Z",
  "aliases" : [ "CVE-2021-26084" ],
  "details" : "In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an authenticated user, and in some instances an unauthenticated user, to execute arbitrary code on a Confluence Server or Data Center instance. The vulnerable endpoints can be accessed by a non-administrator user or unauthenticated user if ‘Allow people to sign up to create their account’ is enabled. To check whether this is enabled go to COG > User Management > User Signup Options. 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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-26084"
  }, {
    "type" : "WEB",
    "url" : "https://jira.atlassian.com/browse/CONFSERVER-67940"
  }, {
    "type" : "WEB",
    "url" : "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26084"
  }, {
    "type" : "WEB",
    "url" : "http://packetstormsecurity.com/files/164013/Confluence-Server-7.12.4-OGNL-Injection-Remote-Code-Execution.html"
  }, {
    "type" : "WEB",
    "url" : "http://packetstormsecurity.com/files/164122/Atlassian-Confluence-WebWork-OGNL-Injection.html"
  }, {
    "type" : "WEB",
    "url" : "http://packetstormsecurity.com/files/167449/Atlassian-Confluence-Namespace-OGNL-Injection.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-74", "CWE-917" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2021-08-30T07:15:00Z"
  }
}