UBUNTU-CVE-2026-55199

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Source
https://ubuntu.com/security/CVE-2026-55199
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-55199
Upstream
  • CVE-2026-55199
Downstream
Related
Published
2026-06-17T20:17:00Z
Modified
2026-06-30T18:17:50.219561927Z
Severity
  • 5.9 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
  • 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
  • Ubuntu - medium
Summary
[none]
Details

libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSHMSGEXTINFO 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 nrextensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from libssh2get_string() are unchecked and the session timeout does not apply to CPU-bound loops.

References

Affected packages

Ubuntu:18.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=bionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.0-1
1.8.0-1ubuntu0.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1",
            "binary_version": "1.8.0-1ubuntu0.1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:20.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=focal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.0-2.1build1
1.8.0-2.1ubuntu0.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1",
            "binary_version": "1.8.0-2.1ubuntu0.1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:22.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.9.0-3
1.10.0-2
1.10.0-2build1
1.10.0-3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1",
            "binary_version": "1.10.0-3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:24.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.11.0-4.1ubuntu0.24.04.2

Affected versions

1.*
1.11.0-2
1.11.0-3
1.11.0-4
1.11.0-4.1build1
1.11.0-4.1build2
1.11.0-4.1ubuntu0.24.04.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1t64",
            "binary_version": "1.11.0-4.1ubuntu0.24.04.2"
        }
    ],
    "availability": "No subscription required"
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:25.10
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.11.1-1ubuntu0.25.10.2

Affected versions

1.*
1.11.1-1
1.11.1-1build1
1.11.1-1ubuntu0.25.10.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1t64",
            "binary_version": "1.11.1-1ubuntu0.25.10.2"
        }
    ],
    "availability": "No subscription required"
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:26.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=resolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.11.1-1ubuntu0.26.04.2

Affected versions

1.*
1.11.1-1build1
1.11.1-1build2
1.11.1-1ubuntu0.26.04.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1t64",
            "binary_version": "1.11.1-1ubuntu0.26.04.2"
        }
    ],
    "availability": "No subscription required"
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:Pro:14.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=esm-infra-legacy%2Ftrusty

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.4.3-1
1.4.3-2
1.4.3-2ubuntu0.1
1.4.3-2ubuntu0.2
1.4.3-2ubuntu0.2+esm1
1.4.3-2ubuntu0.2+esm2
1.4.3-2ubuntu0.2+esm3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1",
            "binary_version": "1.4.3-2ubuntu0.2+esm3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"
Ubuntu:Pro:16.04:LTS
libssh2

Package

Name
libssh2
Purl
pkg:deb/ubuntu/libssh2?arch=source&distro=esm-apps%2Fxenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.5.0-2
1.5.0-2ubuntu0.1
1.5.0-2ubuntu0.1+esm1
1.5.0-2ubuntu0.1+esm2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libssh2-1",
            "binary_version": "1.5.0-2ubuntu0.1+esm2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55199.json"