CVE-2026-66032

libssh2 Double-Free Heap Corruption via sftp_open()

Published Jul 24, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4773-1 libssh2 security update
History
Type Values Removed Values Added
CPEs cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*
Type Values Removed Values Added
First Time appeared Redhat
Redhat hummingbird
Weaknesses CWE-1341
CPEs cpe:/a:redhat:hummingbird:1
Vendors & Products Redhat
Redhat hummingbird
References
Metrics threat_severity

None

threat_severity

Moderate

Type Values Removed Values Added
First Time appeared Libssh2
Libssh2 libssh2
Vendors & Products Libssh2
Libssh2 libssh2
Type Values Removed Values Added
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.
Title libssh2 Double-Free Heap Corruption via sftp_open()
Weaknesses CWE-415
References
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

cvssV4_0

{'score': 8.7, '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'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Nov 10, 2026, 12:49 PM
Reserved
Jul 23, 2026, 8:45 PM
Status
Modified
Published
Jul 24, 2026, 5:17 PM
Modified
Nov 10, 2026, 1:19 PM
Severity
Moderate
Public date
Jul 24, 2026, 4:32 PM