FORTINETVERIFIED
Pre-authentication Denial of Service attack in OpenSSH - CVE-2025-26466
Checked 5 Oct 2026. BlackTree preserves the last verified facts if a later source check is temporarily unavailable.
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PUBLISHER UPDATE · CVE-2025-26466
CVE-2025-26466 release notes and known issues
Pre-authentication Denial of Service attack in OpenSSH - CVE-2025-26466
Scope: Fortinet products. This update record adds version, fix and known-issue context. Its publication date is not a lifecycle boundary.
Summary
CVSSv3 Score: 5.9 CVE-2025-26466A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack. Revised on 2026-05-25 00:00:00
Improvements and security content
- CVSSv3 Score: 5.9 CVE-2025-26466A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack. Revised on 2026-05-25 00:00:00
Known issues
Publisher statementNot stated. The verified publisher record does not contain a known-issues statement.
Affected products and versions
Products
- Fortinet products
Affected versions
- 5.9
Fixed versions or updates
- No fixed version is stated in this record.
Recommended action
Review the official publisher document before deployment.