How severe is CVE-2025-26466?

CVE-2025-26466 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-26466 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 38% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-26466?

CVE-2025-26466 primarily affects Openbsd Openssh. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-26466?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-26466 have an EU (EUVD) identifier?

Yes. CVE-2025-26466 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-5920.

When was CVE-2025-26466 published?

CVE-2025-26466 was published on 2025-02-28 and last updated on 2026-06-30.

CVE-2025-26466

CVE-2025-26466 is a medium-severity vulnerability in Openbsd Openssh with a CVSS 3.x base score of 5.9. Its EPSS exploit-prediction score of 38% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-770.

Key facts

Severity: Medium (CVSS 3.x base score 5.9)
EPSS exploit prediction: 38% (98th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-5920
Weakness: CWE-770
Affected product: Openbsd Openssh
Published: 2025-02-28
Last modified: 2026-06-30

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.

Frequently asked questions

What is CVE-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 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.
How severe is CVE-2025-26466?: CVE-2025-26466 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-26466 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 38% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-26466?: CVE-2025-26466 primarily affects Openbsd Openssh. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-26466?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-26466 have an EU (EUVD) identifier?: Yes. CVE-2025-26466 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-5920.
When was CVE-2025-26466 published?: CVE-2025-26466 was published on 2025-02-28 and last updated on 2026-06-30.

References

Affected products (14)

cpe:2.3:a:openbsd:openssh:9.5:p1:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.6:-:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.6:p1:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.7:-:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.7:p1:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.8:-:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.8:p1:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.9:-:*:*:*:*:*:*
cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:24.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:24.10:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:12.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:13.0:*:*:*:*:*:*:*

More vulnerabilities in Openbsd Openssh

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CVE-2002-0640 — Critical (CVSS 10.0): Buffer overflow in sshd in OpenSSH 2.3.1 through 3.3 may allow remote attackers to execute arbitrary code via a large…
CVE-2001-0144 — Critical (CVSS 10.0): CORE SDI SSH1 CRC-32 compensation attack detector allows remote attackers to execute arbitrary commands on an SSH…
CVE-2000-0999 — Critical (CVSS 10.0): Format string vulnerabilities in OpenBSD ssh program (and possibly other BSD-based operating systems) allow attackers…
CVE-2000-0525 — Critical (CVSS 10.0): OpenSSH does not properly drop privileges when the UseLogin option is enabled, which allows local users to execute…

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Other CWE-770 (Allocation of Resources Without Limits or Throttling) vulnerabilities

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CVE-2020-37067 — Critical (CVSS 9.8): Filetto 1.0 FTP server contains a denial of service vulnerability in the FEAT command processing that allows attackers…
CVE-2021-47875 — Critical (CVSS 9.8): GeoGebra CAS Calculator 6.0.631.0 contains a denial of service vulnerability that allows attackers to crash the…
CVE-2025-11832 — Critical (CVSS 9.8): Allocation of Resources Without Limits or Throttling vulnerability in Azure Access Technology BLU-IC2, Azure Access…
CVE-2024-44241 — Critical (CVSS 9.8): The issue was addressed with improved bounds checks. This issue is fixed in iOS 18.1 and iPadOS 18.1, macOS Sequoia…
CVE-2022-3439 — Critical (CVSS 9.8): Allocation of Resources Without Limits or Throttling in GitHub repository ikus060/rdiffweb prior to 2.5.0.

Browse all CWE-770 (Allocation of Resources Without Limits or Throttling) vulnerabilities →

Threat intelligence

Threat-intel indicators referencing this CVE:

95.59.142.69 (ipv4-addr)
141.98.83.240 (ipv4-addr)
93.89.113.60 (ipv4-addr)
23.251.34.171 (ipv4-addr)
50.6.228.32 (ipv4-addr)
50.35.168.148 (ipv4-addr)
45.123.217.22 (ipv4-addr)
152.53.0.56 (ipv4-addr)