CVE-2026-55200: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-r8mh-x5qv-7gg2
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CVSS 8.1
CWE-680
Published
Advisory Summary

CVE-2026-55200 is a CRITICAL (CVSS 8.1) security vulnerability vulnerability (CWE-680: Integer Overflow to Buffer Overflow) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-55200 at a Glance

CVE Identifier CVE-2026-55200
GHSA Identifier GHSA-r8mh-x5qv-7gg2
Severity CRITICAL
CVSS v3.1 Base Score 8.1
CWE Classification CWE-680: Integer Overflow to Buffer Overflow
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-55200

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-55200, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-680: Integer Overflow to Buffer Overflow, where the product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

References

NVD — CVE-2026-55200 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55200
Software Source Repository REPOSITORY
https://github.com/libssh2/libssh2/pull/2052
Security Fix Commit FIX COMMIT
https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8
Software Source Repository REPOSITORY
https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc
web.archive.org/web/20260623211210/... WEB
https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc
www.vulncheck.com/advisories/libssh2-... WEB
https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c

Frequently Asked Questions

What is CVE-2026-55200?
CVE-2026-55200 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-680: Integer Overflow to Buffer Overflow.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-55200?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-55200?
CVE-2026-55200 has a CVSS v3.1 base score of 8.1 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-55200?
CVE-2026-55200 is classified under CWE-680: Integer Overflow to Buffer Overflow (The product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow.).
How can I check Maven dependencies for CVE-2026-55200?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-r8mh-x5qv-7gg2",
  "modified" : "2026-06-30T15:30:33Z",
  "published" : "2026-06-17T21:34:39Z",
  "aliases" : [ "CVE-2026-55200" ],
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-55200"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/libssh2/libssh2/pull/2052"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc"
  }, {
    "type" : "WEB",
    "url" : "https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-680" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-06-17T20:17:28Z"
  }
}