usn-8486-1
Vulnerability from osv_ubuntu
Published
2026-06-30 12:41
Modified
2026-07-01 20:43
Summary
libssh2 vulnerabilities
Details
It was discovered that libssh2 incorrectly handled the sftp_symlink() function. A malicious SSH server or machine-in-the-middle attacker could possibly use this issue to obtain sensitive information or cause a denial of service. (CVE-2025-15661)
It was discovered that libssh2 had a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler. A malicious SSH server could possibly use this issue to cause a client CPU exhaustion loop, resulting in a denial of service. (CVE-2026-55199)
It was discovered that libssh2 incorrectly handled packet length fields. A remote attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS. (CVE-2026-55200)
References
{
"affected": [
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2025-15661",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
},
{
"id": "CVE-2026-55199",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "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",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:24.04:LTS"
}
},
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "libssh2-1t64",
"binary_version": "1.11.0-4.1ubuntu0.24.04.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "libssh2",
"purl": "pkg:deb/ubuntu/libssh2@1.11.0-4.1ubuntu0.24.04.2?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.11.0-4.1ubuntu0.24.04.2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"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"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2025-15661",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
},
{
"id": "CVE-2026-55199",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "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",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
},
{
"id": "CVE-2026-55200",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:25.10"
}
},
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "libssh2-1t64",
"binary_version": "1.11.1-1ubuntu0.25.10.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "libssh2",
"purl": "pkg:deb/ubuntu/libssh2@1.11.1-1ubuntu0.25.10.2?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.11.1-1ubuntu0.25.10.2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.11.1-1",
"1.11.1-1build1",
"1.11.1-1ubuntu0.25.10.1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2025-15661",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
},
{
"id": "CVE-2026-55199",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "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",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
},
{
"id": "CVE-2026-55200",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:26.04:LTS"
}
},
"ecosystem_specific": {
"availability": "No subscription required",
"binaries": [
{
"binary_name": "libssh2-1t64",
"binary_version": "1.11.1-1ubuntu0.26.04.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "libssh2",
"purl": "pkg:deb/ubuntu/libssh2@1.11.1-1ubuntu0.26.04.2?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.11.1-1ubuntu0.26.04.2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.11.1-1build1",
"1.11.1-1build2",
"1.11.1-1ubuntu0.26.04.1"
]
}
],
"aliases": [],
"details": "It was discovered that libssh2 incorrectly handled the sftp_symlink()\nfunction. A malicious SSH server or machine-in-the-middle attacker could\npossibly use this issue to obtain sensitive information or cause a denial\nof service. (CVE-2025-15661)\n\nIt was discovered that libssh2 had a pre-authentication denial of service\nvulnerability in the SSH_MSG_EXT_INFO handler. A malicious SSH server could\npossibly use this issue to cause a client CPU exhaustion loop, resulting in\na denial of service. (CVE-2026-55199)\n\nIt was discovered that libssh2 incorrectly handled packet length fields. A\nremote attacker could possibly use this issue to execute arbitrary code.\nThis issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS.\n(CVE-2026-55200)",
"id": "USN-8486-1",
"modified": "2026-07-01T20:43:24Z",
"published": "2026-06-30T12:41:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://ubuntu.com/security/notices/USN-8486-1"
},
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2025-15661"
},
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-55199"
},
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-55200"
}
],
"related": [],
"schema_version": "1.7.0",
"summary": "libssh2 vulnerabilities",
"upstream": [
"UBUNTU-CVE-2025-15661",
"UBUNTU-CVE-2026-55199",
"UBUNTU-CVE-2026-55200"
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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