CVE-2026-55200

Published Jun 17, 2026

Last updated 4 hours ago

CVSS critical 9.2
SSH
Port (22)

Overview

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.
Source
disclosure@vulncheck.com
NVD status
Undergoing Analysis

Risk scores

CVSS 4.0

Type
Secondary
Base score
9.2
Impact score
-
Exploitability score
-
Vector string
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Severity
CRITICAL

CVSS 3.1

Type
Secondary
Base score
8.1
Impact score
5.9
Exploitability score
2.2
Vector string
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity
HIGH

Weaknesses

disclosure@vulncheck.com
CWE-680

Social media

Hype score
Not currently trending

  1. libssh2 Client-Side Heap-Overflow RCE (CVE-2026-55200) and Pre-Auth DoS (CVE-2026-55199) Direct: https://t.co/bvz86RVZmo https://t.co/0ipkD4wS4E

    @NewMaxxSSD

    24 Jun 2026

    30 Impressions

    0 Retweets

    0 Likes

    0 Bookmarks

    0 Replies

    0 Quotes

  2. libssh2 CVE-2026-55200 PoC and local RCE scaffold https://t.co/jCH338qRqj #cybersec #threatintel #cve

    @LandscapeThreat

    23 Jun 2026

    30 Impressions

    0 Retweets

    1 Like

    0 Bookmarks

    0 Replies

    0 Quotes

Related CVEs

  1. libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set nr_extensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from _libssh2_get_string() are unchecked and the session timeout does not apply to CPU-bound loops.•CVE-2026-55199
  2. LiteSpeed cPanel Plugin UNIX Symbolic Link (Symlink) Following Vulnerability•CVE-2026-54420
  3. In the Linux kernel, the following vulnerability has been resolved: ptrace: slightly saner 'get_dumpable()' logic The 'dumpability' of a task is fundamentally about the memory image of the task - the concept comes from whether it can core dump or not - and makes no sense when you don't have an associated mm. And almost all users do in fact use it only for the case where the task has a mm pointer. But we have one odd special case: ptrace_may_access() uses 'dumpable' to check various other things entirely independently of the MM (typically explicitly using flags like PTRACE_MODE_READ_FSCREDS). Including for threads that no longer have a VM (and maybe never did, like most kernel threads). It's not what this flag was designed for, but it is what it is. The ptrace code does check that the uid/gid matches, so you do have to be uid-0 to see kernel thread details, but this means that the traditional "drop capabilities" model doesn't make any difference for this all. Make it all make a *bit* more sense by saying that if you don't have a MM pointer, we'll use a cached "last dumpability" flag if the thread ever had a MM (it will be zero for kernel threads since it is never set), and require a proper CAP_SYS_PTRACE capability to override.•CVE-2026-46333
  4. Cisco Catalyst SD-WAN Controller Authentication Bypass Vulnerability•CVE-2026-20182
  5. Linux Kernel Incorrect Resource Transfer Between Spheres Vulnerability•CVE-2026-31431

References

Sources include official advisories and independent security research.