CVE-2026-66032Network attack vector

Client heap corruption via SFTP response double free

Published Jul 24, 2026 · Updated Jul 24, 2026

Double free in libssh2 through 1.11.1 allows remote attackers controlling an SSH server to corrupt a client heap during SFTP open. In sftp_open() in src/sftp.c, an FX_OK status frees the response buffer without clearing its pointer, so a later sftp_packet_require() error frees it again. The client must authenticate to an attacker-controlled server and open an SFTP session; heap corruption can overlap allocations and overwrite function pointers on glibc systems.

CVSS severity8.7
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double free in libssh2 through 1.11.1 allows remote attackers controlling an SSH server to corrupt a client heap during SFTP open. In sftp_open() in src/sftp.c, an FX_OK status frees the response buffer without clearing its pointer, so a later sftp_packet_require() error frees it again. The client must authenticate to an attacker-controlled server and open an SFTP session; heap corruption can overlap allocations and overwrite function pointers on glibc systems.

The record

CVE
CVE-2026-66032
Published
Jul 24, 2026
Updated
Jul 24, 2026
Vendor
libssh2
Product
libssh2
Classifications
CWE-415, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=1.11.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

libssh2 · libssh2version=0 <=1.11.1

Published CVSS scores

8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
8.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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