Fortinet FortiMail: Out-of-bounds write vulnerability (CVE-2026-126154)
An out-of-bounds write vulnerability in multiple Fortinet FortiMail versions allows a remote unauthenticated attacker to cause a denial of service via a crafted HTTP request.
CVE search metadata
CVE search record: CVE-2026-126154. Severity: high. CVSS: 7.5. KEV: no. Product: FortiMail (8.0.0-8.0.1), FortiMail (7.6.0-7.6.6), FortiMail (7.4.0-7.4.8), FortiMail (7.2). Brief: Fortinet FortiMail: Out-of-bounds write vulnerability (CVE-2026-126154). Brief link: https://feed.craftedsignal.io/briefs/2026-11-fortinet-fortimail-oob-write-cve-2026-126154/
Triage facts
Revision 1- Applicability
- FortiMail (8.0.0-8.0.1), FortiMail (7.6.0-7.6.6) +2
- Evidence
- Unknown
- Severity
- Low
- Action
- Elevated
- Sources
- 1 public source
- Freshness
- Revision 1Nov 12, 02:09 UTC
- Vulnerabilities
- 1 CVE
- Source quality
- A1Likely
Fortinet has disclosed an out-of-bounds write vulnerability (CVE-2026-126154) affecting multiple versions of FortiMail. The vulnerability enables a remote, unauthenticated attacker to trigger a denial of service condition by sending a specially crafted HTTP request to an affected device.
Impact
Successful exploitation results in a denial of service, rendering the FortiMail appliance unavailable to process mail or administrative traffic. The base CVSS v3.1 score for this vulnerability is 7.5.
Recommendation
Inventory all FortiMail deployments and monitor for vendor patches to address the vulnerability in the affected versions. Ensure that administrative interfaces are restricted to trusted networks to reduce the attack surface for remote exploitation.
Hunt Leads
Investigate web server logs for anomalous or malformed HTTP requests that precede service disruptions or crashes of the FortiMail appliance. Monitor for spikes in 5xx error codes which may indicate service instability or crashing processes.
Immediate actions
Inventory FortiMail installations and confirm versioning against the affected list.
Threat Hunt
Identify anomalous or malformed HTTP requests directed at FortiMail appliances that correlate with service availability issues.
Data: Web server access logs, System diagnostic logs