CVE-2026-21588

HIGHPre-NVD 7.17.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (19th percentile of EPSS-scored CVEs). 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 — 3 sources updated this week
7.1EG
EchelonGraph verdictPlan mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 7.1Exploit: None knownExposed services: Not assessed

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

This High severity DoS (Denial of Service) vulnerability was introduced in versions 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. 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 9.2.24 Confluence Data Center 10.2: Upgrade to a release greater than or equal to 10.2.17 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.

CVSS v3
7.1
EG Score
7.1HIGHmedium confidence
EG Risk
32
EG Risk 32/100CISA SSVC

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
Severity71% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
19th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 15, 2026

Last Modified

September 16, 2026

Advisory Details (2)

Auto-updated Sep 15, 2026
No patch confirmed yet.
generic

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https://jira.atlassian.com/browse/CONFSERVER-104451
generic

Security Bulletin - September 15 2026 | Atlassian Support | Atlassian Documentation

https://confluence.atlassian.com/pages/viewpage.action?pageId=1822852209

Vendor Advisories for CVE-2026-21588(1)

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

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 27× in last 7d / 81× 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. 2026-10-05 03:11 UTCEG score recompute
  2. 2026-10-05 03:11 UTCGHSA enrichment
  3. 2026-10-04 23:21 UTCEPSS rescore
  4. 2026-10-04 15:35 UTCGHSA enrichment
  5. 2026-10-04 04:09 UTCGHSA enrichment
  6. 2026-10-03 16:44 UTCEG score recompute
  7. 2026-10-03 16:44 UTCGHSA enrichment
  8. 2026-10-03 05:19 UTCGHSA enrichment
  9. 2026-10-02 17:54 UTCEG score recompute
  10. 2026-10-02 17:54 UTCGHSA enrichment
  11. 2026-10-02 06:28 UTCEG score recompute
  12. 2026-10-02 06:28 UTCGHSA enrichment
  13. 2026-10-01 19:49 UTCEPSS rescore
  14. 2026-10-01 19:02 UTCGHSA enrichment
  15. 2026-10-01 06:40 UTCGHSA enrichment
  16. 2026-09-30 19:15 UTCEG score recompute
  17. 2026-09-30 19:15 UTCGHSA enrichment
  18. 2026-09-30 15:03 UTCEPSS rescore
  19. 2026-09-30 07:46 UTCGHSA enrichment
  20. 2026-09-29 20:20 UTCEG score recompute
  21. 2026-09-29 20:19 UTCGHSA enrichment
  22. 2026-09-29 15:21 UTCEPSS rescore
  23. 2026-09-29 07:38 UTCEG score recompute
  24. 2026-09-29 07:38 UTCGHSA enrichment
  25. 2026-09-28 20:13 UTCEG score recompute
Show 56 more
  1. 2026-09-28 20:13 UTCGHSA enrichment
  2. 2026-09-28 13:51 UTCEPSS rescore
  3. 2026-09-28 07:51 UTCGHSA enrichment
  4. 2026-09-27 20:26 UTCEG score recompute
  5. 2026-09-27 20:26 UTCGHSA enrichment
  6. 2026-09-27 13:47 UTCEPSS rescore
  7. 2026-09-27 09:01 UTCGHSA enrichment
  8. 2026-09-26 21:35 UTCEG score recompute
  9. 2026-09-26 21:35 UTCGHSA enrichment
  10. 2026-09-26 15:58 UTCEPSS rescore
  11. 2026-09-26 10:09 UTCEG score recompute
  12. 2026-09-26 10:09 UTCGHSA enrichment
  13. 2026-09-26 00:26 UTCEPSS rescore
  14. 2026-09-25 22:38 UTCGHSA enrichment
  15. 2026-09-25 10:52 UTCGHSA enrichment
  16. 2026-09-24 23:05 UTCEG score recompute
  17. 2026-09-24 23:05 UTCGHSA enrichment
  18. 2026-09-24 14:03 UTCEPSS rescore
  19. 2026-09-24 11:31 UTCGHSA enrichment
  20. 2026-09-24 00:06 UTCEG score recompute
  21. 2026-09-24 00:05 UTCGHSA enrichment
  22. 2026-09-23 12:40 UTCGHSA enrichment
  23. 2026-09-23 01:14 UTCEG score recompute
  24. 2026-09-23 01:14 UTCGHSA enrichment
  25. 2026-09-22 13:48 UTCGHSA enrichment
  26. 2026-09-22 02:23 UTCEG score recompute
  27. 2026-09-22 02:23 UTCGHSA enrichment
  28. 2026-09-21 14:58 UTCGHSA enrichment
  29. 2026-09-21 03:20 UTCEG score recompute
  30. 2026-09-21 03:20 UTCGHSA enrichment
  31. 2026-09-20 20:15 UTCEPSS rescore
  32. 2026-09-20 15:54 UTCGHSA enrichment
  33. 2026-09-20 04:29 UTCGHSA enrichment
  34. 2026-09-19 17:04 UTCEG score recompute
  35. 2026-09-19 17:04 UTCGHSA enrichment
  36. 2026-09-19 05:38 UTCEG score recompute
  37. 2026-09-19 05:38 UTCGHSA enrichment
  38. 2026-09-18 19:27 UTCEPSS rescore
  39. 2026-09-18 18:13 UTCGHSA enrichment
  40. 2026-09-18 06:47 UTCEG score recompute
  41. 2026-09-18 06:47 UTCGHSA enrichment
  42. 2026-09-17 19:21 UTCGHSA enrichment
  43. 2026-09-17 06:41 UTCGHSA enrichment
  44. 2026-09-16 19:12 UTCEG score recompute
  45. 2026-09-16 19:12 UTCGHSA enrichment
  46. 2026-09-16 14:07 UTCEPSS rescore
  47. 2026-09-16 12:00 UTCGHSA enrichment
  48. 2026-09-16 00:35 UTCEG score recompute
  49. 2026-09-16 00:35 UTCGHSA enrichment
  50. 2026-09-15 23:33 UTCEG score recompute
  51. 2026-09-15 23:33 UTCGHSA enrichment
  52. 2026-09-15 18:33 UTCEG score recompute
  53. 2026-09-15 18:33 UTCGHSA enrichment
  54. 2026-09-15 17:32 UTCEG score recompute
  55. 2026-09-15 17:03 UTCEG score recompute
  56. 2026-09-15 17:02 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-21588?
CVE-2026-21588 is a high vulnerability published on September 15, 2026. This High severity DoS (Denial of Service) vulnerability was introduced in versions 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. This DoS (Denial of Service) vulnerability, with a CVSS Score of 7.1, allows an authenticated attacker to cause…
When was CVE-2026-21588 disclosed?
CVE-2026-21588 was first published on September 15, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-21588 actively exploited?
CVE-2026-21588 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (19th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-21588?
CVE-2026-21588 has a CVSS base score of 7.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-21588?
No fix for CVE-2026-21588 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-21588 are linked in the Vendor Advisories panel on this page.

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