CVEvulnerability

CVE-2026-66035

7.7 HIGH Published 2026-07-24 Modified 2026-07-30 Official page ↗
Status
Analyzed
Published
2026-07-24
Last modified
2026-07-30
Assigner
[email protected]
CVSS 4.0 ([email protected])
7.7 HIGH — 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 3.1 ([email protected])
7.5 HIGH — CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weaknesses
CWE-122

Description

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.

Affected configurations

• libssh2 libssh2 (<= 1.11.1)

Related

Weakness · CWE (1)

  • CWE-122 Heap-based Buffer Overflow weakness

References