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CVE-2026-66035 on CTRL-OS 26.05

Aliases: CVE-2026-66035

Packages: libssh2

Status: Plausible

Advisory Information

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.

Updates

2026-07-31 18:05 CEST

Metadata changes:

  • Status for package libssh2: “Plausible”

2026-07-31 18:05 CEST

Metadata changes:

  • Status for package libssh2: “New”