CVE-2026-66035
HIGH
MEDIUM
Priority: 0.04
BB Relevance:
65/100
Published: 2026-07-24
Modified: 2026-11-08
First seen: 2026-11-08
Status: active
Attack Surface
Network
Low Complexity
No Auth
Conf. Impact
Integ. Impact
CVSS Vector Breakdown
AV:
Network
AC:
High
PR:
None
UI:
Passive
S:
X
AT:
None
VC:
High
VI:
High
VA:
High
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.
Weakness Classification (1)
References & Advisories (3)
Patch
Third Party Advisory
Patch
Issue Tracking
Patch