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Report · SecurityWeekAbout CVE-2025-20393Published

China-Linked Hackers Exploiting Zero-Day in Cisco Security Gear

Source SecurityWeek

0
Authoritative record:CVE-2025-20393· Critical 10.0

Exploited in the wild · KEV due 24 Dec 2025 : apply the vendor's fix or mitigations to Cisco Secure Email now.

Data as of 26 Oct 2026, 11:07 UTC

CVSS 3.1 base score
10.0Critical
How severe the flaw is on the 0–10 CVSS scale.
KEV deadline
 US federal agencies must patch by this date; a sensible deadline for everyone else.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 17 Dec 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: evidence found.

    Listed in CISA KEV the same day as disclosure

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by Cisco Systems, Inc.

    , 1.2 years before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. In Threat Radar

    record ingested

    , 14 minutes after disclosure

  4. , the same day as disclosure

  5. KEV remediation due

    US federal deadline

    , 7 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA KEV (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
CiscoCisco Secure EmailAffected
  • 13.0.0-392 – 16.0.1-017
18 affected builds
Fixed in–
CiscoCisco Secure Email and Web ManagerAffected
  • 12.8.1-002 – 16.0.2-088
26 affected builds
Fixed in–
Ciscocisco/cisco-secure-emailpkg:rpm/cisco/cisco-secure-emailOther threatsAffected
  • 13.0.0-392 – 16.0.1-017
18 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until official patches are released, European organizations should implement several specific mitigations: 1) Isolate affected Cisco appliances on segmented network zones with strict access controls to limit lateral movement. 2) Employ enhanced monitoring and logging on these devices to detect anomalous activities indicative of exploitation attempts. 3) Restrict administrative access to the appliances using multi-factor authentication and limit it to trusted personnel only. 4) Deploy network intrusion detection/prevention systems with updated signatures to identify exploit attempts targeting this vulnerability. 5) Conduct thorough audits of appliance configurations and firmware versions to identify potential exposure. 6) Engage with Cisco’s security advisories and apply patches immediately upon release. 7) Educate security teams on indicators of compromise related to this threat and prepare incident response plans tailored to attacks on security infrastructure. 8) Consider temporary compensating controls such as disabling non-essential services or features on the affected appliances to reduce attack surface.

Description

The critical zero-day is tracked as CVE-2025-20393 and it impacts Secure Email Gateway and Secure Email and Web Manager appliances. The post China-Linked Hackers Exploiting Zero-Day in Cisco Security Gear appeared first on SecurityWeek .

References

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