CVE-2025-27915

CRITICALNVD 5.49.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2025-10-07), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 5.4 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 3 sources updated this weekExploited in the wild
9.0EG
EchelonGraph verdictMitigate nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 4.1%CVSS: 5.4Exploit: cisa kev · ssvc active · public exploitExposed services: Not assessed

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

An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.

CVSS v3
5.4
EG Score
9.0CRITICALhigh confidence
EG Risk
81
EG Risk 81/100CISA 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
Severity90% × 45%
Exploitation100% × 40%
Automatability0% × 15%
CISA SSVC: Track at low, Attend at medium and Act at high mission impact.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low, sooner than that at medium and as soon as possible at high mission impact, and watch the vendor's advisory for the fix.
EPSS PROB
4.1%
EPSS %ILE
90th
KEV
⚠ Exploited

CISA SSVCTrack at low, Attend at medium and Act at high mission impact.

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low, sooner than that at medium and as soon as possible at high mission impact, and watch the vendor's advisory for the fix.

Exploitation active (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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

March 12, 2025

Last Modified

November 4, 2025

Advisory Details (6)

Auto-updated Jun 13, 2026
⚠️ Active exploitation confirmed. No fix on record yet. Sources: cisa.
cisa🔴 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-2025-27915
generic🔴 Active Exploitation

0day .ICS attack in the wild | StrikeReady Blog | StrikeReady

https://strikeready.com/blog/0day-ics-attack-in-the-wild/
generic

Zimbra Releases/9.0.0/P44 - Zimbra :: Tech Center

https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes
generic

Zimbra Releases/10.1.5 - Zimbra :: Tech Center

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes
generic

Zimbra Releases/10.0.13 - Zimbra :: Tech Center

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes
generic🔴 Active Exploitation

Security Center - Zimbra :: Tech Center

https://wiki.zimbra.com/wiki/Security_Center

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 56× in last 7d / 255× 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 1,112 total refreshes for this CVE.

  1. 2026-10-09 20:34 UTCEG score recompute
  2. 2026-10-09 20:34 UTCGHSA enrichment
  3. 2026-10-09 20:06 UTCEPSS rescore
  4. 2026-10-09 16:49 UTCGHSA enrichment
  5. 2026-10-09 13:02 UTCGHSA enrichment
  6. 2026-10-09 09:16 UTCGHSA enrichment
  7. 2026-10-09 05:32 UTCGHSA enrichment
  8. 2026-10-09 01:47 UTCGHSA enrichment
  9. 2026-10-08 22:02 UTCGHSA enrichment
  10. 2026-10-08 18:17 UTCEG score recompute
  11. 2026-10-08 18:17 UTCGHSA enrichment
  12. 2026-10-08 17:09 UTCEPSS rescore
  13. 2026-10-08 14:32 UTCGHSA enrichment
  14. 2026-10-08 10:43 UTCGHSA enrichment
  15. 2026-10-08 06:57 UTCGHSA enrichment
  16. 2026-10-08 03:11 UTCEG score recompute
  17. 2026-10-08 03:11 UTCGHSA enrichment
  18. 2026-10-07 23:46 UTCEPSS rescore
  19. 2026-10-07 23:26 UTCGHSA enrichment
  20. 2026-10-07 19:41 UTCGHSA enrichment
  21. 2026-10-07 15:55 UTCGHSA enrichment
  22. 2026-10-07 12:11 UTCGHSA enrichment
  23. 2026-10-07 08:26 UTCGHSA enrichment
  24. 2026-10-07 04:41 UTCGHSA enrichment
  25. 2026-10-07 00:56 UTCGHSA enrichment
Show 75 more
  1. 2026-10-06 21:11 UTCGHSA enrichment
  2. 2026-10-06 17:26 UTCEG score recompute
  3. 2026-10-06 17:26 UTCGHSA enrichment
  4. 2026-10-06 15:16 UTCEPSS rescore
  5. 2026-10-06 13:41 UTCGHSA enrichment
  6. 2026-10-06 09:56 UTCGHSA enrichment
  7. 2026-10-06 06:10 UTCGHSA enrichment
  8. 2026-10-06 02:21 UTCGHSA enrichment
  9. 2026-10-05 22:35 UTCGHSA enrichment
  10. 2026-10-05 18:50 UTCEG score recompute
  11. 2026-10-05 18:50 UTCGHSA enrichment
  12. 2026-10-05 17:42 UTCEPSS rescore
  13. 2026-10-05 15:02 UTCGHSA enrichment
  14. 2026-10-05 11:15 UTCGHSA enrichment
  15. 2026-10-05 07:31 UTCGHSA enrichment
  16. 2026-10-05 03:46 UTCGHSA enrichment
  17. 2026-10-05 00:00 UTCGHSA enrichment
  18. 2026-10-04 20:16 UTCGHSA enrichment
  19. 2026-10-04 16:29 UTCGHSA enrichment
  20. 2026-10-04 12:44 UTCGHSA enrichment
  21. 2026-10-04 08:58 UTCGHSA enrichment
  22. 2026-10-04 05:13 UTCGHSA enrichment
  23. 2026-10-04 01:28 UTCGHSA enrichment
  24. 2026-10-03 21:42 UTCGHSA enrichment
  25. 2026-10-03 17:56 UTCEG score recompute
  26. 2026-10-03 17:56 UTCGHSA enrichment
  27. 2026-10-03 14:24 UTCEPSS rescore
  28. 2026-10-03 14:10 UTCGHSA enrichment
  29. 2026-10-03 10:25 UTCGHSA enrichment
  30. 2026-10-03 06:40 UTCGHSA enrichment
  31. 2026-10-03 02:55 UTCGHSA enrichment
  32. 2026-10-02 23:08 UTCGHSA enrichment
  33. 2026-10-02 19:21 UTCEG score recompute
  34. 2026-10-02 19:21 UTCGHSA enrichment
  35. 2026-10-02 15:35 UTCGHSA enrichment
  36. 2026-10-02 11:49 UTCGHSA enrichment
  37. 2026-10-02 08:05 UTCGHSA enrichment
  38. 2026-10-02 04:20 UTCGHSA enrichment
  39. 2026-10-02 00:34 UTCGHSA enrichment
  40. 2026-10-01 20:49 UTCEG score recompute
  41. 2026-10-01 20:48 UTCGHSA enrichment
  42. 2026-10-01 19:49 UTCEPSS rescore
  43. 2026-10-01 17:03 UTCGHSA enrichment
  44. 2026-10-01 13:18 UTCGHSA enrichment
  45. 2026-10-01 09:33 UTCGHSA enrichment
  46. 2026-10-01 05:48 UTCGHSA enrichment
  47. 2026-10-01 02:03 UTCGHSA enrichment
  48. 2026-09-30 22:17 UTCGHSA enrichment
  49. 2026-09-30 18:32 UTCEG score recompute
  50. 2026-09-30 18:32 UTCGHSA enrichment
  51. 2026-09-30 15:02 UTCEPSS rescore
  52. 2026-09-30 14:46 UTCGHSA enrichment
  53. 2026-09-30 11:01 UTCGHSA enrichment
  54. 2026-09-30 07:14 UTCGHSA enrichment
  55. 2026-09-30 03:29 UTCGHSA enrichment
  56. 2026-09-29 23:42 UTCGHSA enrichment
  57. 2026-09-29 19:57 UTCGHSA enrichment
  58. 2026-09-29 16:11 UTCEG score recompute
  59. 2026-09-29 16:11 UTCGHSA enrichment
  60. 2026-09-29 15:19 UTCEPSS rescore
  61. 2026-09-29 12:26 UTCGHSA enrichment
  62. 2026-09-29 08:41 UTCGHSA enrichment
  63. 2026-09-29 04:56 UTCGHSA enrichment
  64. 2026-09-29 01:11 UTCEG score recompute
  65. 2026-09-29 01:11 UTCGHSA enrichment
  66. 2026-09-28 21:27 UTCGHSA enrichment
  67. 2026-09-28 17:41 UTCGHSA enrichment
  68. 2026-09-28 13:52 UTCGHSA enrichment
  69. 2026-09-28 10:07 UTCGHSA enrichment
  70. 2026-09-28 06:21 UTCGHSA enrichment
  71. 2026-09-28 02:36 UTCGHSA enrichment
  72. 2026-09-27 22:51 UTCGHSA enrichment
  73. 2026-09-27 21:51 UTCCISA KEV update
  74. 2026-09-27 19:06 UTCGHSA enrichment
  75. 2026-09-27 15:21 UTCEG score recompute

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/2025/CVE-2025-27915.yaml
    First seen Jan 1, 2025

    Zimbra - Cross-Site Scripting via ICS Files

    Open source ↗

Related CVEs(same CWE)

Frequently asked(6)

What is CVE-2025-27915?
CVE-2025-27915 is a critical vulnerability published on March 12, 2025. An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its…
When was CVE-2025-27915 disclosed?
CVE-2025-27915 was first published on March 12, 2025, with the most recent update on November 4, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2025-27915 actively exploited?
Yes. CISA added CVE-2025-27915 to the Known Exploited Vulnerabilities catalog on October 7, 2025, affecting Synacor Zimbra Collaboration Suite (ZCS). KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate attention. No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation, and watch the vendor's advisory for the fix.
What is the CVSS score of CVE-2025-27915?
CVE-2025-27915 has a CVSS v3 base score of 5.4 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0 (CRITICAL).
Which products are affected by CVE-2025-27915?
CVE-2025-27915 affects Synacor Zimbra Collaboration Suite (ZCS).
How do I remediate CVE-2025-27915?
No fix for CVE-2025-27915 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.

Dependency Blast Radius

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