DEBIAN-CVE-2026-66035

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Source
https://security-tracker.debian.org/tracker/CVE-2026-66035
Import Source
https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json
JSON Data
https://api.osv.dev/v1/vulns/DEBIAN-CVE-2026-66035
Upstream
Published
2026-07-24T17:17:35.547Z
Modified
2026-07-26T06:00:20.896494543Z
Severity
  • 7.7 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X CVSS Calculator
Summary
[none]
Details

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 packetlength 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 packetlength 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.

References

Affected packages

Debian:11 / libssh2

Package

Name
libssh2
Purl
pkg:deb/debian/libssh2?arch=source&distro=bullseye

Affected ranges

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

Affected versions

1.*
1.9.0-2
1.9.0-2+deb11u1
1.9.0-3
1.10.0-1
1.10.0-2
1.10.0-3
1.11.0-1
1.11.0-2
1.11.0-3
1.11.0-4
1.11.0-4.1~exp1
1.11.0-4.1
1.11.0-5
1.11.0-6
1.11.0-7
1.11.1-1
1.11.1-2
1.11.1-3
1.11.1-4

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json"

Debian:12 / libssh2

Package

Name
libssh2
Purl
pkg:deb/debian/libssh2?arch=source&distro=bookworm

Affected ranges

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

Affected versions

1.*
1.10.0-3
1.11.0-1
1.11.0-2
1.11.0-3
1.11.0-4
1.11.0-4.1~exp1
1.11.0-4.1
1.11.0-5
1.11.0-6
1.11.0-7
1.11.1-1
1.11.1-2
1.11.1-3
1.11.1-4

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json"

Debian:13 / libssh2

Package

Name
libssh2
Purl
pkg:deb/debian/libssh2?arch=source&distro=trixie

Affected ranges

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

Affected versions

1.*
1.11.1-1
1.11.1-1+deb13u1
1.11.1-2
1.11.1-3
1.11.1-4

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json"

Debian:14 / libssh2

Package

Name
libssh2
Purl
pkg:deb/debian/libssh2?arch=source&distro=forky

Affected ranges

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

Affected versions

1.*
1.11.1-1
1.11.1-2
1.11.1-3
1.11.1-4

Ecosystem specific 

{
    "urgency": "not yet assigned"
}

Database specific

source 
"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-66035.json"