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Public PoC Released for Critical libssh2 CVE-2026-55200 Client-Side SSH Flaw

Aggregated by BrevFeed security · updated 93d ago
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Key points

  • CVE-2026-55200 allows memory corruption via malicious SSH servers.
  • Affects all libssh2 versions up to 1.11.1.
  • Exploit code published in a GitHub archive.

Overview of CVE-2026-55200

CVE-2026-55200 is a critical vulnerability in libssh2 that could enable memory corruption on a client connecting to a malicious or compromised SSH server. It is classified with a CVSS score of 9.2, indicating a severe risk. The flaw affects every release of libssh2 up to and including version 1.11.1.

How the Vulnerability Works

The vulnerability stems from the function ssh2_transport_read() in the source file transport.c. It fails to enforce an upper limit on the packet_length field when parsing SSH packets, which can lead to integer overflow. This oversight can trigger an out-of-bounds heap write, a known method for potential code execution.

Patch and Public PoC Release

The flaw was reported by security researcher Tristan Madani, and the fix was merged into the codebase on June 12, with VulnCheck publishing the CVE on June 17. A public proof-of-concept for this exploit is now available in 'exploitarium,' which provides various code that could lead to remote code execution under specific conditions.

Impact and Implications

Given that libssh2 is embedded in numerous applications including curl, Git, and PHP, many systems and devices utilizing these libraries are at risk, particularly those that connect to untrusted SSH endpoints. The prevalence of statically linked libraries may hinder automatic updates to address this vulnerability.

✨ This summary was generated by AI from the outlets' reporting listed below. It is not independently verified and may contain errors — check the original sources. How BrevFeed works →

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Primary sources

CVE CVE-2019-38558.8 HIGH CVE CVE-2025-156616.5 MEDIUM CVE CVE-2026-551995.9 MEDIUM CVE CVE-2026-552008.1 HIGH

Reporting from

The Hacker News — Public PoC Released for Critical libssh2 CVE-2026-55200 Client-Side SSH Flaw 95d ago →

A public proof-of-concept has been released for CVE-2026-55200, a critical flaw in libssh2 that may allow memory corruption and code execution for connected clients. This vulnerability affects all versions up to 1.11.1, posing significant risks as libssh2 is widely used in various applications and systems.