Medium Denial of service

CVE-2026-21577 — Uncontrolled Resource Consumption in Atlassian Confluence Data Center

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.

Published Jul 21, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: atlassian

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Atlassian

Confluence Data Center

CVSS base

6.5

Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Atlassian Confluence Data Center).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Atlassian	Confluence Data Center	version 10.2.0 to 10.2.6version 9.0.1 to 9.0.3version 9.1.0 to 9.1.1version 9.2.0 to 9.2.15version 9.3.1 to 9.3.2version 9.4.0 to 9.4.1version 9.5.1 to 9.5.4version 10.0.2 to 10.0.3 and 1 more version 10.1.0 to 10.1.2	Vulnerable	CVE Program (cve.org) e CISA ADP
Atlassian	Confluence Data Center	≥ 9.0.1 and ≤ 9.0.3≥ 10.2.0 and ≤ 10.2.6≥ 10.1.0 and ≤ 10.1.2≥ 10.0.2 and ≤ 10.0.3≥ 9.5.1 and ≤ 9.5.4≥ 9.4.0 and ≤ 9.4.1≥ 9.3.1 and ≤ 9.3.2≥ 9.2.0 and ≤ 9.2.15 and 1 more ≥ 9.1.0 and ≤ 9.1.1	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.1	CVSS 4.0	High	—	—	security@atlassian.com via NIST National Vulnerability Database
7.1	CVSS 4.0	High	—	—	atlassian via CVE Program (cve.org) e CISA ADP
6.5	CVSS 3.1	Medium	2.8	3.6	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-400 · Uncontrolled Resource Consumption

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Track CPU/memory spikes and availability drops correlated with request patterns.

web/proxy/WAF logsnetwork IDS/IPSresource metrics

Timeline

What happened to this CVE, newest first.

2026
Affected products added · atlassian/confluence data center
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 6.5
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Jul 21, 2026 · atlassian

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

2 on the record

confluence.atlassian.com/pages/viewpage.action
Vendor Advisory, NIST National Vulnerability Database
jira.atlassian.com/browse/CONFSERVER-104334
Issue Tracking, NIST National Vulnerability Database

Elsewhere on this site

Atlassian
every CVE for this vendor

Denial of service
same class

CWE-400
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-21589 Atlassian Multiple Products Files or Directories Accessible to External Parties Vulnerability KEV 10d
High CVE-2026-21586 Improper Authorization in Atlassian Confluence Data Center Sep 15, 2026
High CVE-2026-21579 Exposure of Sensitive Information in Atlassian Confluence Data Center Jul 21, 2026
High CVE-2025-22166 This High severity DoS (Denial of Service) vulnerability was introduced in version 2.0… Oct 21, 2025
Critical CVE-2023-22527 Atlassian Confluence Data Center and Server Template Injection Vulnerability KEV Jan 16, 2024
Critical CVE-2023-22518 Atlassian Confluence Data Center and Server Improper Authorization Vulnerability KEV Oct 31, 2023

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-21577 is "Uncontrolled Resource Consumption in Atlassian Confluence Data Center", rated Medium. It affects Confluence Data Center (Atlassian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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