CVE-2026-76519: Cisco Secure Email Gateway Relative Path Traversal Vulnerability

In short

Cisco Secure Email Gateway has a weakness classified as relative path traversal (CWE-23). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-10-14. NVD lists CVSS 3.1 at 9.8 CRITICAL.

What it is

“Cisco Secure Email Gateway contains a relative path traversal vulnerability that could allow an unauthenticated, remote attacker to write arbitrary files on the underlying operating system.” — CISA KEV, retrieved 2026-11-01

“A vulnerability in the Advanced Malware Protection (AMP) feature of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to write arbitrary files on the underlying operating system. This vulnerability is due to improper handling of email attachments when the file reputation service is enabled. An attacker could exploit this vulnerability by sending an email that contains a crafted attachment through an affected device. A successful exploit could allow the attacker to write arbitrary files and execute commands with root privileges on the underlying operating system.” — NVD, retrieved 2026-11-01

Who is affected

Cisco Secure Email Gateway. NVD lists the following versions as affected:

• Versions from 15.0 inclusive, before 15.5.5-014
• Versions from 16.0 inclusive, before 16.5.0-780

Exploitation status

CISA KEV added: 2026-10-14. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-10-17.

Scores

NVD CVSS 3.1: 9.8 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source [email protected].

EPSS by FIRST: 2.15%; percentile 82.15; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-23.

Timeline

CISA required action

“Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.” — CISA KEV

What to do

• Confirm whether you run Cisco Secure Email Gateway and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-afw-zqYJkjxp
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.