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Ubuntu 26.04 LTS libssh2 Important DoS Remote Code Exec USN-8486-1

ubuntu
Calendar Grey June 30, 2026
Dist Ubuntu Esm H88
Multiple security flaws have been addressed in libssh2 affecting multiple Ubuntu versions. Update recommended to ensure security.
Several security issues were fixed in libssh2.

Summary

Several security issues were fixed in libssh2.

Software Description:

- libssh2: Client-side C library implementing the SSH2 protocol

Details:

It was discovered that libssh2 incorrectly handled the sftp_symlink()

function. A malicious SSH server or machine-in-the-middle attacker could

possibly use this issue to obtain sensitive information or cause a denial

of service. (CVE-2025-15661)

It was discovered that libssh2 had a pre-authentication denial of service

vulnerability in the SSH_MSG_EXT_INFO handler. A malicious SSH server could

possibly use this issue to cause a client CPU exhaustion loop, resulting in

a denial of service. (CVE-2026-55199)

It was discovered that libssh2 incorrectly handled packet length fields. A

remote attacker could possibly use this issue to execute arbitrary code.

This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS.

(CVE-2026-55200)

Topics%20covered

Topics Covered

security advisory denial of service remote code execution Ubuntu important libssh2

Update Instructions

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
  libssh2-1t64                    1.11.1-1ubuntu0.26.04.2

Ubuntu 25.10
  libssh2-1t64                    1.11.1-1ubuntu0.25.10.2

Ubuntu 24.04 LTS
  libssh2-1t64                    1.11.0-4.1ubuntu0.24.04.2

In general, a standard system update will make all the necessary changes.

References

https://ubuntu.com/security/notices/USN-8486-1

CVE-2025-15661, CVE-2026-55199, CVE-2026-55200

Severity
important
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-8486-1

Topics%20covered

Topics Covered

security advisory denial of service remote code execution Ubuntu important libssh2

Package Information

https://launchpad.net/ubuntu/+source/libssh2/1.11.1-1ubuntu0.26.04.2
https://launchpad.net/ubuntu/+source/libssh2/1.11.1-1ubuntu0.25.10.2
https://launchpad.net/ubuntu/+source/libssh2/1.11.0-4.1ubuntu0.24.04.2

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