How severe is CVE-2021-26084?

CVE-2021-26084 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-26084 being actively exploited?

Yes. CVE-2021-26084 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-26084?

CVE-2021-26084 primarily affects Atlassian Confluence Data Center. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-26084?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-26084 have an EU (EUVD) identifier?

Yes. CVE-2021-26084 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-12905. It is also flagged as exploited in the EUVD (since 2021-11-03).

When was CVE-2021-26084 published?

CVE-2021-26084 was published on 2021-08-30 and last updated on 2026-06-17.

CVE-2021-26084

CVE-2021-26084 is a critical-severity vulnerability in Atlassian Confluence Data Center with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2021-11-03). The underlying weakness is classified as CWE-917.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 100% (100th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2021-11-03)
EU (EUVD) id: EUVD-2021-12905
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2021-11-03)
Weakness: CWE-917
Affected product: Atlassian Confluence Data Center
Published: 2021-08-30
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-26084?: 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.
How severe is CVE-2021-26084?: CVE-2021-26084 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-26084 being actively exploited?: Yes. CVE-2021-26084 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-26084?: CVE-2021-26084 primarily affects Atlassian Confluence Data Center. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-26084?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-26084 have an EU (EUVD) identifier?: Yes. CVE-2021-26084 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-12905. It is also flagged as exploited in the EUVD (since 2021-11-03).
When was CVE-2021-26084 published?: CVE-2021-26084 was published on 2021-08-30 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:atlassian:confluence_data_center:*:*:*:*:*:*:*:*
cpe:2.3:a:atlassian:confluence_server:*:*:*:*:*:*:*:*

More vulnerabilities in Atlassian Confluence Data Center

CVE-2023-22527 — Critical (CVSS 9.8): A template injection vulnerability on older versions of Confluence Data Center and Server allows an unauthenticated…
CVE-2023-22518 — Critical (CVSS 9.8): All versions of Confluence Data Center and Server are affected by this unexploited vulnerability. This Improper…
CVE-2023-22515 — Critical (CVSS 9.8): Atlassian has been made aware of an issue reported by a handful of customers where external attackers may have…
CVE-2022-26136 — Critical (CVSS 9.8): A vulnerability in multiple Atlassian products allows a remote, unauthenticated attacker to bypass Servlet Filters used…
CVE-2022-26134 — Critical (CVSS 9.8): In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an…
CVE-2024-21683 — High (CVSS 8.8): This High severity RCE (Remote Code Execution) vulnerability was introduced in version 5.2 of Confluence Data Center…

All CVEs affecting Atlassian Confluence Data Center →

Other CWE-917 vulnerabilities

CVE-2025-3322 — Critical (CVSS 10.0): An improper neutralization of inputs used in expression language allows remote code execution with the highest…
CVE-2022-22947 — Critical (CVSS 10.0): In spring cloud gateway versions prior to 3.1.1+ and 3.0.7+ , applications are vulnerable to a code injection attack…
CVE-2026-52439 — Critical (CVSS 9.8): An issue in xiandafu beetl 3.20.2 allows a remote attacker to execute arbitrary code via the type.new function and the…
CVE-2026-11561 — Critical (CVSS 9.8): Improper neutralization of special elements used in an expression language statement ('expression language injection')…
CVE-2026-22738 — Critical (CVSS 9.8): In Spring AI, a SpEL injection vulnerability exists in SimpleVectorStore when a user-supplied value is used as a…
CVE-2026-24713 — Critical (CVSS 9.8): Improper Input Validation vulnerability in Apache IoTDB. This issue affects Apache IoTDB: from 1.0.0 before 1.3.7,…

Browse all CWE-917 vulnerabilities →