Medium
Openssh: denial-of-service in openssh
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2025-26466
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 5 Nov 2026, 01:33 UTC · Revision 1
Source evidence
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.
osv:CVE-2025-26466
Complete source record
{
"id": "d13e168f40edf065e34353053b93c5e9d07411d35ebc5c3714cea5d8f826e010",
"url": "https://osv.dev/vulnerability/CVE-2025-26466",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Openssh: denial-of-service in openssh",
"summary": "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.",
"evidence": "osv:CVE-2025-26466",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2025-26466",
"aliases": [
"CVE-2025-26466"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/openssh/openssh-portable",
"type": "GIT",
"events": [
{
"introduced": "80a2f64b8c1d27383cc83d182b73920d1e6a91f1"
},
{
"last_affected": "53a80baaebda180f46e6e8571f3ff800e1f5c496"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.5:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "9.5-p1"
},
{
"last_affected": "9.5-p1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.6:-:*:*:*:*:*:*",
"range": [
{
"introduced": "9.6-NA"
},
{
"last_affected": "9.6-NA"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.6:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "9.6-p1"
},
{
"last_affected": "9.6-p1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.7:-:*:*:*:*:*:*",
"range": [
{
"introduced": "9.7-NA"
},
{
"last_affected": "9.7-NA"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.7:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "9.7-p1"
},
{
"last_affected": "9.7-p1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.8:-:*:*:*:*:*:*",
"range": [
{
"introduced": "9.8-NA"
},
{
"last_affected": "9.8-NA"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.8:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "9.8-p1"
},
{
"last_affected": "9.8-p1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:openbsd:openssh:9.9:p1:*:*:*:*:*:*",
"range": [
{
"introduced": "9.9-p1"
},
{
"last_affected": "9.9-p1"
}
],
"source": "CPE_STRING"
}
]
}
}
],
"versions": [
"9.5-p1",
"9.6-NA",
"9.7-NA",
"9.8-NA",
"9.9-p1",
"V_9_5_P1",
"V_9_9_P1",
"V_9_7_P1",
"V_9_6_P1"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-26466.json"
}
}
],
"modified": "2026-10-28T02:30:41.197240250Z",
"provider": "osv",
"references": [
"https://access.redhat.com/downloads/content/package-browser/",
"https://cert-portal.siemens.com/productcert/html/ssa-398330.html",
"https://seclists.org/oss-sec/2025/q1/144",
"https://security-tracker.debian.org/tracker/CVE-2025-26466",
"https://ubuntu.com/security/CVE-2025-26466",
"https://www.openssh.com/",
"https://www.openwall.com/lists/oss-security/2025/02/18/1",
"https://www.openwall.com/lists/oss-security/2025/02/18/4",
"https://www.qualys.com/2025/02/18/openssh-mitm-dos.txt",
"https://www.vicarius.io/vsociety/posts/cve-2025-26466-detection-script-memory-consumption-vulnerability-in-openssh",
"https://www.vicarius.io/vsociety/posts/cve-2025-26466-mitigation-script-memory-consumption-vulnerability-in-openssh",
"https://access.redhat.com/errata/RHBA-2025:6305",
"https://access.redhat.com/errata/RHSA-2025:6993",
"https://access.redhat.com/security/cve/CVE-2025-26466",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/26xxx/CVE-2025-26466.json",
"https://nvd.nist.gov/vuln/detail/CVE-2025-26466",
"https://security.netapp.com/advisory/ntap-20250228-0002/",
"https://bugzilla.redhat.com/show_bug.cgi?id=2345043",
"https://bugzilla.suse.com/show_bug.cgi?id=1237041",
"https://anongit.mindrot.org/openssh.git"
],
"provider_metadata": {
"cwe_ids": [
"CWE-770"
],
"cna_assigner": "redhat",
"unresolved_ranges": [
{
"extracted_events": [
{
"range": [
{
"fixed": "0:9.9p1-7.el10_0"
},
{
"fixed": "0:8.7p1-45.el9"
},
{
"fixed": "0:8.7p1-45.el9"
}
],
"source": "AFFECTED_FIELD",
"strategy": "InverseAffectedRanges"
}
]
},
{
"extracted_events": [
{
"range": [
{
"introduced": "9.5p1"
},
{
"last_affected": "9.9p1"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
}
]
}
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/26xxx/CVE-2025-26466.json"
}
},
"related_cves": [
{
"value": "CVE-2025-26466",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 509110,
"published_at": "2025-02-28T21:25:28.861+00:00"
}