OpenSSH Memory Consumption Vulnerability - CVE-2025-26466
Summary
CVE-2025-26466: A flaw was found in the OpenSSH package. Affects openssh across 6 version ranges.
< 9.6_p1-r2
< 53a80baaebda180f46e6e8571f3ff800e1f5c496
< 80a2f64b8c1d27383cc83d182b73920d1e6a91f1
< 86bdd3853f4d32c85e295e6216a2fe0953ad93f0
< 8241b9c0529228b4b86d88b1a6076fb9f97e4a99
< 6849957945754e6551e515f41e8cf3937cda222d
Fixed in 9.6_p1-r2. How to fix ↓
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Background
OpenSSH is a widely used suite of secure networking utilities based on the SSH protocol, allowing secure remote login and other secure network services. It is known for its robust security features and is commonly deployed in various operating systems. However, a recent vulnerability has been identified that affects its memory management, potentially leading to denial of service.
Vulnerability Detail
A flaw was found in the OpenSSH package where each ping packet received by the SSH server results in the allocation of a pong packet in a memory buffer. This pong packet is stored in a queue and is only freed after the server/client key exchange is completed. A malicious client can exploit this by continuously sending ping packets, causing an uncontrolled increase in memory consumption on the server side. This can lead to server unavailability, resulting in a denial of service attack.
How To Fix
Minimum fixed version
9.6_p1-r2
This is the first release that contains the fix.
sudo apk add --upgrade opensshTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, consider implementing rate limiting on the SSH server to mitigate the impact of excessive ping packets from malicious clients. This can be done by configuring the server's firewall or using SSH configuration options to limit the number of allowed connections.
Conclusion
The OpenSSH vulnerability CVE-2025-26466 poses a significant risk due to its potential for denial of service attacks through memory consumption issues. It is essential to update to the latest patched versions of OpenSSH to protect against this vulnerability and ensure the security and availability of your systems.
See every vulnerability recorded for openssh →
FAQ
CVE-2025-26466 is a vulnerability in the OpenSSH package that allows a malicious client to exploit memory management issues, potentially leading to denial of service.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The main consequence is an uncontrolled increase in memory consumption on the server, which can lead to server unavailability and denial of service.
Yes, patches are available for various versions of OpenSSH. It is crucial to update to the specified patched versions to mitigate the vulnerability.
The CVSS score for CVE-2025-26466 is 5.9, indicating a moderate severity level.
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