CVE-2026-55199

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Source
https://cve.org/CVERecord?id=CVE-2026-55199
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55199.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-55199
Downstream
ALPINE (1)
AZL (1)
BELL (1)
CGA (6)
DEBIAN (1)
ECHO (1)
JLSEC (1)
MGASA (1)
MINI (1)
OESA (4)
openSUSE (2)
RHSA (1)
ROOT (1)
SUSE (8)
UBUNTU (1)
Related
CGA (1)
openSUSE (2)
SUSE (8)
Published
2026-06-17T18:44:18Z
Modified
2026-08-26T18:27:58Z
Severity
  • 8.2 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N CVSS Calculator
Summary
libssh2 - Pre-Authentication DoS via SSH_MSG_EXT_INFO Handler
Details

libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set nr_extensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from _libssh2_get_string() are unchecked and the session timeout does not apply to CPU-bound loops.

Database specific 
{
    "cna_assigner":  "VulnCheck",
    "cwe_ids":  [
        "CWE-835"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55199.json"
}
References

Affected packages

Git / github.com/libssh2/libssh2

Affected ranges

Type
GIT
Repo
https://github.com/libssh2/libssh2
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
17626857d20b3c9a1addfa45979dadcee1cd84a4
Database specific
Show details 
{
    "cpe":  "cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*",
    "extracted_events":  [
        {
            "introduced":  "0"
        },
        {
            "last_affected":  "1.11.1"
        }
    ],
    "source":  [
        "CPE_RANGE",
        "REFERENCES"
    ]
}

Affected versions

RELEASE.*
RELEASE.0.1
RELEASE.0.10
RELEASE.0.11
RELEASE.0.12
RELEASE.0.13
RELEASE.0.14
RELEASE.0.15
RELEASE.0.16
RELEASE.0.17
RELEASE.0.18
RELEASE.0.3
RELEASE.0.5
RELEASE.0.6
RELEASE.0.7
RELEASE.0.8
RELEASE.1.0
RELEASE.1.1
beforenb-0.*
beforenb-0.14
beforenb2-0.*
beforenb2-0.14
libssh2-1.*
libssh2-1.10.0
libssh2-1.11.0
libssh2-1.11.1
libssh2-1.2
libssh2-1.2.1
libssh2-1.2.3
libssh2-1.2.4
libssh2-1.2.5
libssh2-1.2.6
libssh2-1.2.7
libssh2-1.2.8
libssh2-1.2.9
libssh2-1.3.0
libssh2-1.4.0
libssh2-1.4.1
libssh2-1.4.2
libssh2-1.4.3
libssh2-1.5.0
libssh2-1.6.0
libssh2-1.7.0
libssh2-1.8.0
libssh2-1.9.0

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55199.json"
vanir_signatures 
[
    {
        "deprecated":  false,
        "digest":  {
            "line_hashes":  [
                "67122845657668344552371962070822576711",
                "149606929713965925426466961564282333041",
                "192278621762336052757313921640537879588",
                "138666448627037029192090976022784337754",
                "333614903892572360934878653345642136656"
            ],
            "threshold":  0.9
        },
        "id":  "CVE-2026-55199-00f7cd61",
        "signature_type":  "Line",
        "signature_version":  "v1",
        "source":  "https://github.com/libssh2/libssh2/commit/17626857d20b3c9a1addfa45979dadcee1cd84a4",
        "target":  {
            "file":  "src/packet.c"
        }
    },
    {
        "deprecated":  false,
        "digest":  {
            "function_hash":  "202695723005422450388970061283937754254",
            "length":  16686
        },
        "id":  "CVE-2026-55199-da3d9784",
        "signature_type":  "Function",
        "signature_version":  "v1",
        "source":  "https://github.com/libssh2/libssh2/commit/17626857d20b3c9a1addfa45979dadcee1cd84a4",
        "target":  {
            "file":  "src/packet.c",
            "function":  "_libssh2_packet_add"
        }
    }
]
vanir_signatures_modified 
"2026-08-12T16:09:46Z"