ZeroDayAlert

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

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.

Cisco Secure Email Gateway Added to KEV 2026-10-14 Federal due 2026-10-17 Known ransomware use

Required action — quoted from CISA

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.

Where this comes from. The identifier, product, dates and required action above are copied verbatim from the CISA Known Exploited Vulnerabilities catalog. The action plan below is written by an AI agent from that record and published automatically. AssurePort has not independently tested this vulnerability and makes no claim about whether any specific system is affected.

Who is affected

Cisco Secure Email Gateway deployments are vulnerable to unauthenticated remote file write via a relative path traversal flaw. This affects both on-premises and cloud-hosted instances. The record does not specify which versions, release dates, or patch status apply to this vulnerability.

How to check whether this touches you

  • Inventory your email security infrastructure: identify all Cisco Secure Email Gateway instances, their deployment model (on-premises or cloud), and their network location.
  • Establish external reachability: confirm whether each instance accepts traffic directly from the internet or is behind a perimeter proxy or firewall.
  • Query the running build: log into each appliance and retrieve the software version and patch level from the administrative interface; version strings alone are a signal, not definitive proof of exposure, as backported fixes may exist in older release tracks.
  • Check Cisco's advisory for this CVE for the specific version ranges and patch identifiers applicable to your instances.

What to do

  1. Immediately consult Cisco's published guidance for CVE-2026-76519, including patch availability, supported upgrade paths, and any interim mitigations.
  2. If patches are not yet available, evaluate whether you can restrict network access to the appliance (for example, via firewall rules, VPN gating, or removal from direct internet exposure).
  3. If the appliance cannot be protected by access controls and no patch exists, escalate to your security leadership and email operations teams to discuss discontinuing use pending remediation, as stated in the required action.
  4. Enable and retain all available logs from the Secure Email Gateway (connection logs, file system access logs, administrative actions) with sufficient retention to support forensic review if exploitation is suspected.
  5. Follow CISA's BOD 26-04 guidance for patching timelines based on this vulnerability's risk to your organisation.

If you find you were exposed

Exploitation of arbitrary file write typically occurs before public disclosure, so you should search logs backwards from the publication date (14 October 2026) for evidence of requests that contain path traversal sequences or attempts to write to unexpected file paths. Verify the integrity of critical email gateway configuration and authentication files. Determine how long your logs are retained; if retention is shorter than the window between vulnerability introduction and discovery, confirm the appliance's filesystem for signs of tampering or added files.

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Knowing it exists is not the same as knowing you are exposed.

This page can tell you that CVE-2026-76519 is being exploited. It cannot tell you whether Secure Email Gateway is running somewhere of yours that is reachable. That question is what a scan answers.

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