How severe is CVE-2026-21577?

CVE-2026-21577 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-21577 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-21577?

CVE-2026-21577 affects Atlassian Confluence Data Center. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-21577?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-21577 published?

CVE-2026-21577 was published on 2026-07-21 and last updated on 2026-08-10.

CVE-2026-21577

CVE-2026-21577 is a medium-severity vulnerability in Atlassian Confluence Data Center with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 7.1
EPSS exploit prediction: 0% (16th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-400
Affected product: Atlassian Confluence Data Center
Published: 2026-07-21
Last modified: 2026-08-10

Description

This High severity DoS (Denial of Service) vulnerability was introduced in versions 9.0.1, 9.1.0, 9.2.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0 and 10.2.0 of Confluence Data Center. This DoS (Denial of Service) vulnerability, with a CVSS Score of 7.1, allows an authenticated attacker to cause a resource to be unavailable for its intended users by temporarily or indefinitely disrupting services of a host connected to a network. Atlassian recommends that Confluence Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions: Confluence Data Center 9.2: Upgrade to a release greater than or equal to 9.2.17 Confluence Data Center 10.2: Upgrade to a release greater than or equal to 10.2.7 See the release notes ([https://confluence.atlassian.com/doc/confluence-release-notes-327.html]). You can download the latest version of Confluence Data Center from the download center ([https://www.atlassian.com/software/confluence/download-archives]). This vulnerability was reported via our Penetration Testing program.

Frequently asked questions

What is CVE-2026-21577?: This High severity DoS (Denial of Service) vulnerability was introduced in versions 9.0.1, 9.1.0, 9.2.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0 and 10.2.0 of Confluence Data Center. This DoS (Denial of Service) vulnerability, with a CVSS Score of 7.1, allows an authenticated attacker to cause a resource to be unavailable for its intended users by temporarily or indefinitely disrupting services of a host connected to a network. Atlassian recommends that Confluence Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions: Confluence Data Center 9.2: Upgrade to a release greater than or equal to 9.2.17 Confluence Data Center 10.2: Upgrade to a release greater than or equal to 10.2.7 See the release notes ([https://confluence.atlassian.com/doc/confluence-release-notes-327.html]). You can download the latest version of Confluence Data Center from the download center ([https://www.atlassian.com/software/confluence/download-archives]). This vulnerability was reported via our Penetration Testing program.
How severe is CVE-2026-21577?: CVE-2026-21577 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-21577 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-21577?: CVE-2026-21577 affects Atlassian Confluence Data Center. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-21577?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-21577 published?: CVE-2026-21577 was published on 2026-07-21 and last updated on 2026-08-10.

References

Affected products (1)

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

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-2021-26084 — Critical (CVSS 9.8): In affected versions of Confluence Server and Data Center, an OGNL injection vulnerability exists that would allow an…

All CVEs affecting Atlassian Confluence Data Center →

Other CWE-400 (Uncontrolled Resource Consumption) vulnerabilities

CVE-2026-46775 — Critical (CVSS 9.9): Vulnerability in Oracle REST Data Services (component: Core). Supported versions that are affected are 24.2.0-26.1.0.…
CVE-2025-61303 — Critical (CVSS 9.8): Hatching Triage Sandbox Windows 10 build 2004 (2025-08-14) and Windows 10 LTSC 2021(2025-08-14) contains a…
CVE-2025-43193 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15.6, macOS Sonoma 14.7.7,…
CVE-2025-24269 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15.4. An app may be able to…
CVE-2025-24264 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in Safari 18.4, iOS 18.4 and iPadOS 18.4,…
CVE-2025-24260 — Critical (CVSS 9.8): The issue was addressed with improved memory handling. This issue is fixed in macOS Sequoia 15.4, macOS Sonoma 14.7.5,…

Browse all CWE-400 (Uncontrolled Resource Consumption) vulnerabilities →