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

Quick assessment

Affected
libssh2 libssh2
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

libssh2是libssh2团队开源的一款实现SSH2协议的客户端C库。 libssh2 1.11.1及之前版本存在资源管理错误漏洞，该漏洞源于sftp_open()函数中存在双重释放，可能导致恶意SSH服务器破坏任何打开SFTP会话的已验证客户端的堆。

CVSS 8.8 · High EPSS 0.45% · P36

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 2

VendorProduct Version RangeStatus
libssh2 libssh2 ≤ 1.11.1 affected
5e4776146552d898b9c0e1b313cd093fa8dc92d0 unaffected
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I. Basic Information for CVE-2026-66032

Vulnerability Information
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Vulnerability Title
libssh2 Double-Free Heap Corruption via sftp_open()
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
双重释放
Source: CVE Program / CVE List V5
Vulnerability Title
libssh2 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
libssh2是libssh2团队开源的一款实现SSH2协议的客户端C库。 libssh2 1.11.1及之前版本存在资源管理错误漏洞，该漏洞源于sftp_open()函数中存在双重释放，可能导致恶意SSH服务器破坏任何打开SFTP会话的已验证客户端的堆。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
libssh2 libssh2 0 ~ 1.11.1 -

II. Public POCs for CVE-2026-66032

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Success marker: VULNERABLE: glibc tcache double-free abort in libssh2 sftp_open(): 'free(): double free detected in tcache 2' (client exit=134)
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
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claude_code · 12488 chars
GitHub 复现环境（可 clone 直接跑）
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III. Intelligence Information for CVE-2026-66032

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Patches & Fixes for CVE-2026-66032 (2)

Vendor Advisories for CVE-2026-66032 (1)

Same Patch Batch · libssh2 · 2026-07-24 · 4 CVEs total

CVE-2026-66033 7.5 HIGH libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation
CVE-2026-66034 7.5 HIGH libssh2 Heap Out-of-Bounds Read via publickey subsystem
CVE-2026-66035 7.5 HIGH libssh2 Heap Buffer Overflow via ETM Cipher Negotiation

IV. Related Vulnerabilities

Same product: libssh2
Same vendor: libssh2
Same weakness: CWE-415

V. Comments for CVE-2026-66032

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