CVE-2026-66032

Description

libssh2 through 1.11.1, fixed in commit 5e47761, contains a double-free vulnerability in the sftp_open() function in src/sftp.c that allows a malicious SSH server to corrupt the heap of any authenticated client opening an SFTP session. When a server responds to SSH_FXP_OPEN with SSH_FXP_STATUS containing FX_OK, the response data buffer is freed, and if a subsequent sftp_packet_require() call returns a specific error such as LIBSSH2_ERROR_CHANNEL_PACKET_EXCEEDED, the same pointer is freed a second time, enabling tcache dup conditions on glibc systems that allow overlapping allocations and function pointer overwrites.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libssh2	26.04 LTS resolute	Fixed 1.11.1-1ubuntu0.26.04.4
	24.04 LTS noble	Fixed 1.11.0-4.1ubuntu0.24.04.4
	22.04 LTS jammy	Fixed 1.10.0-3ubuntu0.1
	20.04 LTS focal	Fixed 1.8.0-2.1ubuntu0.1+esm1
	18.04 LTS bionic	Fixed 1.8.0-1ubuntu0.1+esm1
	16.04 LTS xenial	Fixed 1.5.0-2ubuntu0.1+esm3
	14.04 LTS trusty	Fixed 1.4.3-2ubuntu0.2+esm4

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Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
libssh2	Upstream: 5e47761

Severity score breakdown

CVSS version:

Base score 8.7 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Attack requirements	None
Privileges required	None
User interaction	Passive
Vulnerable system - Confidentiality impact	High
Vulnerable system - Integrity impact	High
Vulnerable system - Availability impact	High
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	None

Scores

Parameter	Value
Base score	8.7 · High
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

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

Base score 8.8 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Unchanged
Confidentiality impact	High
Integrity impact	High
Availability impact	High

Scores

Parameter	Value
Base score	8.8 · High
Exploitability score	-
Impact score	-

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

References

Related Ubuntu Security Notices (USN)

USN-8722-1
libssh2 vulnerabilities
3 September 2026

USN-8799-1
libssh2 vulnerabilities
22 September 2026