DEBIAN-CVE-2026-66035
libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packet_length smaller than the cipher's block size during Encrypt-then-MAC cipher negotiation. In the fullpacket() function in src/transport.c, the ETM path allocates a buffer of packet_length bytes but copies blocksize minus one bytes via memcpy, causing an overflow that on 32-bit glibc writes attacker-controlled bytes into an adjacent chunk's SIZE field, enabling tcache bin confusion, overlapping live objects, and function pointer overwrite during the session handshake before authentication.
DEBIAN-CVE-2026-66035
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-2026-66035
libssh2
Source reference: /affected/0/package/name
- Affected versions
- 1.11.1-1
Source reference:
/affected/0/versions1.11.1-1+deb13u1Source reference:
/affected/0/versions - Fixed versions
- 1.11.1-1+deb13u2
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/versions1.11.1-4Source reference:
/affected/1/versions - Fixed versions
- 1.11.1-5
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+deb13u2"
}
]
}
],
"package": {
"name": "libssh2",
"purl": "pkg:deb/debian/libssh2?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1.11.1-1",
"1.11.1-1+deb13u1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.11.1-5"
}
]
}
],
"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",
"1.11.1-4"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #58271 · Revision 1
- Added to Heist Feed
- Publisher date