DEBIAN-CVE-2026-55199
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.
DEBIAN-CVE-2026-55199
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-55199
libssh2
Source reference: /affected/0/package/name
- Affected versions
- 1.11.1-1
Source reference:
/affected/0/versions - Fixed versions
- 1.11.1-1+deb13u1
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
libssh2
Source reference: /affected/1/package/name
- Affected versions
- 1.11.1-1
Source reference:
/affected/1/versions1.11.1-2Source reference:
/affected/1/versions1.11.1-3Source reference:
/affected/1/versions - Fixed versions
- 1.11.1-4
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.11.1-1+deb13u1"
}
]
}
],
"package": {
"name": "libssh2",
"purl": "pkg:deb/debian/libssh2?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1.11.1-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55199.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.11.1-4"
}
]
}
],
"package": {
"name": "libssh2",
"purl": "pkg:deb/debian/libssh2?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"1.11.1-1",
"1.11.1-2",
"1.11.1-3"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55199.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #57341 · Revision 1
- Added to Heist Feed
- Publisher date