CVE-2024-27443

CRITICALNVD 6.19.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2025-05-19), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 6.1 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 4 sources updated this weekExploited in the wild
9.0EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 24%CVSS: 6.1Exploit: cisa kev · ssvc active · epss top5pct · public exploitExposed: 0

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

An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in the CalendarInvite feature of the Zimbra webmail classic user interface, because of improper input validation in the handling of the calendar header. An attacker can exploit this via an email message containing a crafted calendar header with an embedded XSS payload. When a victim views this message in the Zimbra webmail classic interface, the payload is executed in the context of the victim's session, potentially leading to execution of arbitrary JavaScript code.

CVSS v3
6.1
EG Score
9.0(high)
EG Risk
81(Attend)
EG Risk 81/100SSVC: Attend

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
Severity90% × 45%
Exploitation100% × 40%
Automatability0% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
24%
EPSS %ILE
98%
KEV
⚠ Exploited

Published

August 12, 2024

Last Modified

October 31, 2025

Advisory Details (4)

Auto-updated Jun 13, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cisa.
generic🔴 Active Exploitation

Operation RoundPress targeting high-value webmail servers

https://www.welivesecurity.com/en/eset-research/operation-roundpress/
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-27443
generic

Zimbra Releases/9.0.0/P39 - Zimbra :: Tech Center

https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes
generic

Zimbra Releases/10.0.7 - Zimbra :: Tech Center

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 57× in last 7d / 251× 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.

Showing the most recent 100 of 943 total refreshes for this CVE.

  1. 2026-09-22 14:46 UTCEPSS rescore
  2. 2026-09-22 14:22 UTCGHSA enrichment
  3. 2026-09-22 10:24 UTCGHSA enrichment
  4. 2026-09-22 06:26 UTCGHSA enrichment
  5. 2026-09-22 02:28 UTCGHSA enrichment
  6. 2026-09-21 22:30 UTCEG score recompute
  7. 2026-09-21 22:30 UTCGHSA enrichment
  8. 2026-09-21 19:09 UTCCISA KEV update
  9. 2026-09-21 18:32 UTCGHSA enrichment
  10. 2026-09-21 14:34 UTCGHSA enrichment
  11. 2026-09-21 10:36 UTCGHSA enrichment
  12. 2026-09-21 06:38 UTCGHSA enrichment
  13. 2026-09-21 02:40 UTCGHSA enrichment
  14. 2026-09-20 22:41 UTCGHSA enrichment
  15. 2026-09-20 18:43 UTCGHSA enrichment
  16. 2026-09-20 14:45 UTCGHSA enrichment
  17. 2026-09-20 10:47 UTCGHSA enrichment
  18. 2026-09-20 06:48 UTCGHSA enrichment
  19. 2026-09-20 02:47 UTCGHSA enrichment
  20. 2026-09-19 22:49 UTCGHSA enrichment
  21. 2026-09-19 18:51 UTCEG score recompute
  22. 2026-09-19 18:51 UTCGHSA enrichment
  23. 2026-09-19 15:40 UTCEPSS rescore
  24. 2026-09-19 14:53 UTCGHSA enrichment
  25. 2026-09-19 10:54 UTCGHSA enrichment
Show 75 more
  1. 2026-09-19 06:56 UTCGHSA enrichment
  2. 2026-09-19 02:58 UTCGHSA enrichment
  3. 2026-09-18 22:59 UTCEG score recompute
  4. 2026-09-18 22:59 UTCGHSA enrichment
  5. 2026-09-18 19:26 UTCEPSS rescore
  6. 2026-09-18 19:20 UTCCISA KEV update
  7. 2026-09-18 19:01 UTCGHSA enrichment
  8. 2026-09-18 15:03 UTCGHSA enrichment
  9. 2026-09-18 14:15 UTCCISA KEV update
  10. 2026-09-18 11:04 UTCGHSA enrichment
  11. 2026-09-18 07:06 UTCGHSA enrichment
  12. 2026-09-18 03:08 UTCGHSA enrichment
  13. 2026-09-17 23:10 UTCEG score recompute
  14. 2026-09-17 23:10 UTCGHSA enrichment
  15. 2026-09-17 19:11 UTCGHSA enrichment
  16. 2026-09-17 15:13 UTCGHSA enrichment
  17. 2026-09-17 11:15 UTCGHSA enrichment
  18. 2026-09-17 07:16 UTCGHSA enrichment
  19. 2026-09-17 03:18 UTCGHSA enrichment
  20. 2026-09-16 23:19 UTCGHSA enrichment
  21. 2026-09-16 19:20 UTCGHSA enrichment
  22. 2026-09-16 15:22 UTCEG score recompute
  23. 2026-09-16 15:22 UTCGHSA enrichment
  24. 2026-09-16 14:10 UTCCISA KEV update
  25. 2026-09-16 14:06 UTCEPSS rescore
  26. 2026-09-16 14:06 UTCEPSS rescore
  27. 2026-09-16 11:24 UTCGHSA enrichment
  28. 2026-09-16 07:25 UTCEG score recompute
  29. 2026-09-16 07:25 UTCGHSA enrichment
  30. 2026-09-16 03:26 UTCGHSA enrichment
  31. 2026-09-15 23:28 UTCGHSA enrichment
  32. 2026-09-15 19:30 UTCGHSA enrichment
  33. 2026-09-15 15:31 UTCGHSA enrichment
  34. 2026-09-15 11:33 UTCGHSA enrichment
  35. 2026-09-15 07:35 UTCGHSA enrichment
  36. 2026-09-15 03:36 UTCEG score recompute
  37. 2026-09-15 03:36 UTCGHSA enrichment
  38. 2026-09-15 03:08 UTCEPSS rescore
  39. 2026-09-15 03:08 UTCEPSS rescore
  40. 2026-09-14 23:38 UTCGHSA enrichment
  41. 2026-09-14 19:40 UTCGHSA enrichment
  42. 2026-09-14 19:24 UTCCISA KEV update
  43. 2026-09-14 15:42 UTCGHSA enrichment
  44. 2026-09-14 11:43 UTCGHSA enrichment
  45. 2026-09-14 07:45 UTCGHSA enrichment
  46. 2026-09-14 03:47 UTCGHSA enrichment
  47. 2026-09-13 23:49 UTCGHSA enrichment
  48. 2026-09-13 19:51 UTCEG score recompute
  49. 2026-09-13 19:51 UTCGHSA enrichment
  50. 2026-09-13 16:45 UTCEPSS rescore
  51. 2026-09-13 15:53 UTCGHSA enrichment
  52. 2026-09-13 11:55 UTCGHSA enrichment
  53. 2026-09-13 07:56 UTCGHSA enrichment
  54. 2026-09-13 03:58 UTCGHSA enrichment
  55. 2026-09-13 00:00 UTCGHSA enrichment
  56. 2026-09-12 20:02 UTCGHSA enrichment
  57. 2026-09-12 16:04 UTCEG score recompute
  58. 2026-09-12 16:04 UTCGHSA enrichment
  59. 2026-09-12 14:59 UTCEPSS rescore
  60. 2026-09-12 12:06 UTCGHSA enrichment
  61. 2026-09-12 08:08 UTCGHSA enrichment
  62. 2026-09-12 04:09 UTCGHSA enrichment
  63. 2026-09-12 00:11 UTCGHSA enrichment
  64. 2026-09-11 20:12 UTCGHSA enrichment
  65. 2026-09-11 18:49 UTCCISA KEV update
  66. 2026-09-11 16:14 UTCEG score recompute
  67. 2026-09-11 16:14 UTCGHSA enrichment
  68. 2026-09-11 14:51 UTCEPSS rescore
  69. 2026-09-11 12:16 UTCEG score recompute
  70. 2026-09-11 12:16 UTCGHSA enrichment
  71. 2026-09-11 09:35 UTCEPSS rescore
  72. 2026-09-11 08:18 UTCGHSA enrichment
  73. 2026-09-11 04:20 UTCGHSA enrichment
  74. 2026-09-11 00:21 UTCGHSA enrichment
  75. 2026-09-10 20:23 UTCGHSA enrichment

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2024/CVE-2024-27443.yaml
    First seen Jan 1, 2024

    Zimbra Collaboration - Cross-Site Scripting (XSS)

    Open source ↗

Related CVEs(same CWE)

Frequently asked(6)

What is CVE-2024-27443?
CVE-2024-27443 is a critical vulnerability published on August 12, 2024. An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in the CalendarInvite feature of the Zimbra webmail classic user interface, because of improper input validation in the handling of the calendar header. An attacker can exploit this…
When was CVE-2024-27443 disclosed?
CVE-2024-27443 was first published in the National Vulnerability Database on August 12, 2024, with the most recent update on October 31, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2024-27443 actively exploited?
Yes. CISA added CVE-2024-27443 to the Known Exploited Vulnerabilities catalog on May 19, 2025, affecting Synacor Zimbra Collaboration Suite (ZCS). KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2024-27443?
CVE-2024-27443 has a CVSS v3 base score of 6.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
Which products are affected by CVE-2024-27443?
CVE-2024-27443 affects Synacor Zimbra Collaboration Suite (ZCS). The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2024-27443?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2024-27443, 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.

Dependency Blast Radius

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