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Findings

CVE-2025-26466

A flaw was found in the OpenSSH package.

Published Feb 28, 2025 · corrected/updated Oct 15, 2026 · openbsd openssh · evidence confidence high

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.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2025-26466 is a medium public vulnerability record for openbsd openssh. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether openbsd openssh is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: canonical/ubuntu linux (24.04); debian/debian linux (11.0); openbsd/openssh (9.5); openbsd/openssh (9.6). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 5.9, EPSS 40.6%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-770. Sources contributing to this record: cve_org, epss, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 28, 2025 · NIST NVD

    Detected

    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

  2. Oct 15, 2026 · NIST NVD

    Updated

    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

Affected

  • cpe canonical/ubuntu linux24.04
  • cpe debian/debian linux11.0
  • cpe openbsd/openssh9.5
  • cpe openbsd/openssh9.6
  • cpe openbsd/openssh9.7
  • cpe openbsd/openssh9.8
  • cpe openbsd/openssh9.9

Sources

  • CVE.orgVulnerability recordCVE-2025-26466

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-26466

    30-day exploitation probability 40.6%

    first.org
  • NIST NVDVulnerability recordCVE-2025-26466

    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 pack

    nvd.nist.gov

References