CVE-2026-66034

Publication date 24 July 2026

Last updated 2 September 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

7.5 · High

Score breakdown

Description

libssh2 through 1.11.1, fixed in commit a13bb6c, contains a missing bounds check vulnerability that allows a malicious SSH server to trigger an arbitrary-length heap out-of-bounds read and a free of an uninitialized pointer via the publickey subsystem. In libssh2_publickey_list_fetch(), the version 1 response parser reads a server-controlled comment_len value and advances the parse pointer without verifying sufficient bytes remain in the buffer, causing the out-of-bounds read to leak heap pointers from adjacent allocations defeating ASLR, followed by heap allocator state corruption when the error cleanup path frees an uninitialized pointer from a non-zeroed realloc() region.

Read the notes from the security team

Status

Package Ubuntu Release Status
libssh2 26.04 LTS resolute
Fixed 1.11.1-1ubuntu0.26.04.3
24.04 LTS noble
Fixed 1.11.0-4.1ubuntu0.24.04.3
22.04 LTS jammy
Vulnerable
20.04 LTS focal
Vulnerable
18.04 LTS bionic
Vulnerable
16.04 LTS xenial
Vulnerable
14.04 LTS trusty
Vulnerable

Notes

mdeslaur

This commit was mistriaged as CVE-2026-58051 and included in USN-8532-1 as CVE-2026-58051.patch

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
libssh2

Severity score breakdown

CVSS version:

Base score 7.7 · High

Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Base score 7.5 · High

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

References

Related Ubuntu Security Notices (USN)

    • USN-8799-1
    • libssh2 vulnerabilities
    • 22 September 2026

Other references

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