CVE-2026-21580

CRITICALPre-NVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 71% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 5 sources updated this week
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.3Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

This Critical severity Stored XSS, PrivEsc (Privilege Escalation), and Security Misconfiguration vulnerability was introduced in versions 7.1.1, 7.4.0, 7.13.0, 7.17.0, 7.19.0, 8.0.0, 8.5.0, 8.9.0, 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 and Server. This Stored XSS, PrivEsc (Privilege Escalation), and Security Misconfiguration vulnerability, with a CVSS Score of 8.6, allows an unauthenticated attacker to execute arbitrary HTML or JavaScript code on a victims browser, perform actions as a higher-privileged user, and to get into the system utilizing loopholes exposed from security best-practices being overlooked. Atlassian recommends that Confluence Data Center and Server 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 and Server 9.2: Upgrade to a release greater than or equal to 9.2.21 Confluence Data Center and Server 10.2: Upgrade to a release greater than or equal to 10.2.13 See the release notes ([https://confluence.atlassian.com/doc/confluence-release-notes-327.html]). You can download the latest version of Confluence Data Center and Server from the download center ([https://www.atlassian.com/software/confluence/download-archives]). This vulnerability was reported via our Bug Bounty program.

CVSS v3
9.3
EG Score
9.3(medium)
EG Risk
57(Track)
EG Risk 57/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity93% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
29%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 21, 2026

Advisory Details (2)

Auto-updated Aug 18, 2026
No patch confirmed yet.
generic

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https://jira.atlassian.com/browse/CONFSERVER-104381
generic

Security Bulletin - August 18 2026 | Atlassian Support | Atlassian Documentation

https://confluence.atlassian.com/pages/viewpage.action?pageId=1821999768

Vendor Advisories for CVE-2026-21580(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Data Freshness Timeline

(refreshed 32× in last 7d / 32× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-21 04:36 UTCEG score recompute▲ 0.70
  2. 2026-08-21 04:36 UTCGHSA enrichment
  3. 2026-08-21 04:34 UTCNVD updateCVSS v3 → 9.3 · CVSS v4 → 9.3 · severity → CRITICAL
  4. 2026-08-21 04:02 UTCEG score recompute▼ 0.70
  5. 2026-08-21 04:01 UTCGHSA enrichment
  6. 2026-08-21 03:59 UTCMITRE cvelistV5CVSS v3 → 8.6 · CVSS v4 → 8.6 · severity → HIGH
  7. 2026-08-21 00:34 UTCEG score recompute
  8. 2026-08-21 00:34 UTCGHSA enrichment
  9. 2026-08-20 22:55 UTCEPSS rescore
  10. 2026-08-20 20:36 UTCGHSA enrichment
  11. 2026-08-20 16:38 UTCEG score recompute▲ 0.70
  12. 2026-08-20 16:38 UTCGHSA enrichment
  13. 2026-08-20 16:30 UTCNVD updateCVSS v3 → 9.3 · CVSS v4 → 9.3 · severity → CRITICAL
  14. 2026-08-20 15:46 UTCEG score recompute▼ 0.70
  15. 2026-08-20 15:46 UTCGHSA enrichment
  16. 2026-08-20 15:41 UTCMITRE cvelistV5CVSS v3 → 8.6 · CVSS v4 → 8.6 · severity → HIGH
  17. 2026-08-20 14:02 UTCGHSA enrichment
  18. 2026-08-20 10:04 UTCGHSA enrichment
  19. 2026-08-20 06:07 UTCGHSA enrichment
  20. 2026-08-20 02:09 UTCGHSA enrichment
  21. 2026-08-19 22:11 UTCGHSA enrichment
  22. 2026-08-19 18:13 UTCEG score recompute
  23. 2026-08-19 18:13 UTCGHSA enrichment
  24. 2026-08-19 17:03 UTCEPSS rescore
  25. 2026-08-19 14:14 UTCGHSA enrichment
Show 7 more
  1. 2026-08-19 10:17 UTCGHSA enrichment
  2. 2026-08-19 06:19 UTCGHSA enrichment
  3. 2026-08-19 02:21 UTCGHSA enrichment
  4. 2026-08-18 22:23 UTCEG score recompute▲ 0.70
  5. 2026-08-18 22:22 UTCNVD updateCVSS v3 → 9.3 · CVSS v4 → 9.3 · severity → CRITICAL
  6. 2026-08-18 22:04 UTCEG score recompute
  7. 2026-08-18 22:04 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-21580?
CVE-2026-21580 is a critical vulnerability published on August 18, 2026. This Critical severity Stored XSS, PrivEsc (Privilege Escalation), and Security Misconfiguration vulnerability was introduced in versions 7.1.1, 7.4.0, 7.13.0, 7.17.0, 7.19.0, 8.0.0, 8.5.0, 8.9.0, 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 and…
When was CVE-2026-21580 disclosed?
CVE-2026-21580 was first published in the National Vulnerability Database on August 18, 2026, with the most recent update on August 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-21580 actively exploited?
CVE-2026-21580 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 71.2% of all scored CVEs.
What is the CVSS score of CVE-2026-21580?
CVE-2026-21580 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-21580?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-21580, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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