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Fortinet PSIRT AdvisoriesFG-IR-25-122

Pre-authentication Denial of Service attack in OpenSSH - CVE-2025-26466

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

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5.9CVSS out of 10Medium severity
Scope

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  1. Published by Fortinet

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  2. Updated by Fortinet

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CVEs named in this advisory

CVE-2025-26466View CVSS, KEV, EPSS, and threat context
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