Is CVE-2026-55200 actively exploited?

No active exploitation of CVE-2026-55200 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-55200 be exploited remotely?

Yes. CVE-2026-55200 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-55200?

CVE-2026-55200 has a CVSS score of 8.1 (HIGH).

HOME VULNERABILITIESCVE-2026-55200

HIGH

CVE-2026-55200

CWE-680Published: June 17, 2026· Updated: Jun 22, 2026

8.1

CVSS v3.1

Official Description

libssh2 through 1.11.1, fixed in commit 7acf3df contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.

NVD Source

Technical Analysis

CVE-2026-55200 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.1.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges Req.None

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time

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News & Research Mentioning CVE-2026-55200

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

The Hacker News· Jun 29, 2026

A public proof-of-concept is now out for CVE-2026-55200, a critical flaw in libssh2 that lets a malicious or compromised SSH server trigger memory corruption on a connecting client, with possible code execution. No credentials, no user interaction. The bug affects every release up to and including 1.11.1 and carries a CVSS 4.0 score of 9.2. libssh2 is a client-side SSH library, not a server. [xlite_meta score:53 src:The Hacker News xlite_fp:d3aaa6617c1f4d441fa3e6610c0d98efbd919e2cc4a772cf6dc397b812624bc6]