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Vulnerability · Published Jul 24, 2026 · Assigned by VulnCheck

CVE-2026-66032libssh2 Double-Free Heap Corruption via sftp_open()

High 8.8

In plain English

A high-severity double free in libssh2 from libssh2. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High
Exploit odds (30 days)0.4%top 60.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.21libssh21.11.1-r3ALPINE-CVE-2026-66032
Alpine:v3.22libssh21.11.1-r3ALPINE-CVE-2026-66032
Alpine:v3.23libssh21.11.1-r4ALPINE-CVE-2026-66032
Alpine:v3.24libssh21.11.1-r4ALPINE-CVE-2026-66032
Debian:12libssh21.10.0-3+deb12u1DEBIAN-CVE-2026-66032
Debian:13libssh21.11.1-1+deb13u2DEBIAN-CVE-2026-66032
Debian:14libssh21.11.1-5DEBIAN-CVE-2026-66032
Ubuntu:22.04:LTSlibssh21.10.0-3ubuntu0.1USN-8799-1
Ubuntu:22.04:LTSlibssh21.10.0-3ubuntu0.1UBUNTU-CVE-2026-66032
Ubuntu:24.04:LTSlibssh21.11.0-4.1ubuntu0.24.04.4USN-8722-1
Ubuntu:24.04:LTSlibssh21.11.0-4.1ubuntu0.24.04.4UBUNTU-CVE-2026-66032
Ubuntu:26.04:LTSlibssh21.11.1-1ubuntu0.26.04.4USN-8722-1
Ubuntu:26.04:LTSlibssh21.11.1-1ubuntu0.26.04.4UBUNTU-CVE-2026-66032

Affected products (as reported)

VendorProductVersions
libssh2 libssh2 0 – through 1.11.1

Weakness: CWE-415 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References