CVE-2026-76519 · High · CISA KEV

Cisco Secure Email Gateway Path Traversal: Critical for Email Infrastructure Defense

Threat Engine Auto-Feed · data current as of 2026-10-15

A relative path traversal vulnerability in Cisco Secure Email Gateway (CVE-2026-76519) allows unauthenticated, remote attackers to write arbitrary files to the underlying operating system. This vulnerability is actively exploited in the wild, as confirmed by its inclusion in CISA's KEV catalog, indicating a high immediate risk to affected organizations. Its EPSS score is in the 77th percentile, further underscoring the elevated likelihood of exploitation.

  • CVSS:
  • EPSS percentile: 0.77354
  • Exploitation pressure: 71/100 (High)

Exploitation reality: listed in CISA KEV (exploited in the wild) · EPSS 77th percentile. Threat × Vulnerability from public signals — impact depends on your environment.

Weakness —

Relative path traversal occurs when an application constructs a file path using user-supplied input without properly sanitizing or validating it. An attacker can inject special characters like '..' (dot-dot-slash) to navigate outside the intended directory and access or create files in arbitrary locations on the server's file system.

Who's at risk

Exposure: unknown · Auth: unknown · unknown

Enterprise profiles most at risk

  • Organizations using Cisco Secure Email Gateway for critical email infrastructure
  • Financial services organizations
  • Technology sector organizations

Misconfigurations that escalate it

  • Lack of robust file integrity monitoring on critical systems
  • Insufficient network segmentation isolating email gateway appliances

High-impact scenarios

  • Remote code execution via arbitrary file write, leading to full system compromise
  • Disruption of email services and communication
  • Data exfiltration or modification from the compromised gateway
  • Establishment of persistent access within the network perimeter

Likely adversaries

  • FIN7 — Financial services (Assessed)
  • LockBit affiliates — Financial services (Assessed)
  • APT38 (Lazarus) — Financial services (Assessed)
  • APT29 (Cozy Bear) — Technology (Assessed)
  • Scattered Spider — Technology (Assessed)

What to do (defensive)

Detect

  • Monitor Cisco Secure Email Gateway logs for unusual file write operations or access patterns.
  • Implement file integrity monitoring (FIM) on the underlying operating system of the gateway to detect unauthorized file changes.
  • Scan network perimeters for vulnerable Cisco Secure Email Gateway versions.

Contain

  • Isolate affected Cisco Secure Email Gateway appliances from the broader network.
  • Block suspicious inbound connections to the gateway if anomalous activity is detected.

Patch

  • Apply vendor-provided security patches for Cisco Secure Email Gateway (CVE-2026-76519) immediately upon availability.

Frontier verdict — High

This is a critical vulnerability in Cisco Secure Email Gateway, actively exploited in the wild, enabling unauthenticated remote arbitrary file writes, demanding immediate patching.

For detection-engineering and awareness only · point-in-time · not security advice · sourced from NVD, FIRST EPSS, CISA KEV. Adversary mappings are assessments unless cited.