CVE-2026-55200 PUBLISHED

libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c

Assigner: VulnCheck
Reserved: 16.06.2026 Published: 17.06.2026 Updated: 18.06.2026

libssh2 through 1.11.1, fixed in commit 7acf3df contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS Score: 9.2

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	Present	Availability	High	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 8.1

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	libssh2
Product	libssh2
Versions	Default: unaffected affected from 0 to 1.11.1 (incl.) Version 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8 is unaffected

CVE-2026-55200 PUBLISHED

libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c

Metrics

Product Status

Credits

References

Problem Types