CVE-2025-26466: Allocation of Resources Without Limits or Throttling
A 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.
AI Analysis
Technical Summary
This vulnerability in OpenSSH 9.5p1 involves allocation of resources without limits or throttling. For each ping packet received, the SSH server allocates a pong packet in memory and queues it until the server/client key exchange finishes. Because these allocations are not freed promptly, a malicious client can send numerous ping packets, causing uncontrolled memory growth on the server side. This can exhaust server memory and result in denial of service. The CVSS 3.1 score is 5.9 (medium), reflecting network attack vector, high attack complexity, no privileges required, no user interaction, and impact limited to availability.
Potential Impact
The vulnerability allows an unauthenticated remote attacker to cause a denial of service by exhausting server memory through repeated ping packets. There is no impact on confidentiality or integrity, but availability of the SSH server can be disrupted.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The Red Hat advisory URL is provided but does not explicitly mention a fix or workaround. Until a patch is available, consider limiting incoming SSH connections or applying rate limiting on ping packets if possible.
CVE-2025-26466: Allocation of Resources Without Limits or Throttling
Description
A 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.
CVSS v3.1
Score 5.9medium
Affected software
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability in OpenSSH 9.5p1 involves allocation of resources without limits or throttling. For each ping packet received, the SSH server allocates a pong packet in memory and queues it until the server/client key exchange finishes. Because these allocations are not freed promptly, a malicious client can send numerous ping packets, causing uncontrolled memory growth on the server side. This can exhaust server memory and result in denial of service. The CVSS 3.1 score is 5.9 (medium), reflecting network attack vector, high attack complexity, no privileges required, no user interaction, and impact limited to availability.
Potential Impact
The vulnerability allows an unauthenticated remote attacker to cause a denial of service by exhausting server memory through repeated ping packets. There is no impact on confidentiality or integrity, but availability of the SSH server can be disrupted.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The Red Hat advisory URL is provided but does not explicitly mention a fix or workaround. Until a patch is available, consider limiting incoming SSH connections or applying rate limiting on ping packets if possible.
Technical Details
- Data Version
- 5.1
- Assigner Short Name
- redhat
- Date Reserved
- 2025-02-10T18:31:47.979Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2025-26466","vendor":"Red Hat"}]
Threat ID: 6835dda5182aa0cae2186687
Added to database: 05/27/2025, 15:43:33 UTC
Last enriched: 07/02/2026, 22:09:57 UTC
Last updated: 09/10/2026, 19:36:49 UTC
Views: 138
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