CVE-2026-66035
HIGH
7,7
Source: [email protected]
Attack Vector: network
Attack Complexity: high
Privileges Required: none
User Interaction: passive
Confidentiality: N/A
Integrity: N/A
Availability: N/A
HIGH
7,5
Source: [email protected]
Attack Vector: network
Attack Complexity: high
Privileges Required: none
User Interaction: required
Scope: unchanged
Confidentiality: high
Integrity: high
Availability: high
Description
AI Translation Available
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.
122
Heap-based Buffer Overflow
DraftCommon Consequences
Security Scopes Affected:
Availability
Integrity
Confidentiality
Access Control
Other
Potential Impacts:
Dos: Crash, Exit, Or Restart
Dos: Resource Consumption (Cpu)
Dos: Resource Consumption (Memory)
Execute Unauthorized Code Or Commands
Bypass Protection Mechanism
Modify Memory
Other
Applicable Platforms
Languages:
Memory-Unsafe, C, C++
https://github.com/libssh2/libssh2/commit/42e33d81577ed4b95d4b4f6f845e5ee8efe5e…
https://github.com/libssh2/libssh2/pull/2198
https://www.vulncheck.com/advisories/libssh2-heap-buffer-overflow-via-etm-ciphe…