CVE-2026-44040: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-j37g-g7hg-vhg6
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CVSS 4.8
CWE-338
Published
Advisory Summary

CVE-2026-44040 is a MODERATE (CVSS 4.8) security vulnerability vulnerability (CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product uses a pseudo-random number generator (prng) in a security context, but the prng's algorithm is not cryptographically strong.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-44040 at a Glance

CVE Identifier CVE-2026-44040
GHSA Identifier GHSA-j37g-g7hg-vhg6
Severity MODERATE
CVSS v3.1 Base Score 4.8
CWE Classification CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 4.8

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:L/I:L/A:N).

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 Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-44040

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-2026-44040, 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-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG), where the product uses a pseudo-random number generator (prng) in a security context, but the prng's algorithm is not cryptographically strong. 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

UltraVNC through 1.8.2.2 uses a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes() function seeds libc rand() with time(0) + getpid() + rand() and generates a 16-byte challenge. The combined seed space is approximately 31 bits (libc rand() internal state) and is entirely determined by publicly-observable values (wall-clock time and process ID). An attacker who can observe the authentication exchange can enumerate the seed space and predict the challenge within seconds, enabling forgery or offline brute-forcing of responses. Note: on Windows, the active code path may use vncEncryptBytes2.cpp which calls CryptGenRandom; reachability on shipped Windows binaries requires compile-graph verification and is under investigation.

References

NVD — CVE-2026-44040 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44040
Software Source Repository REPOSITORY
https://github.com/ultravnc/UltraVNC
uvnc.com WEB
https://uvnc.com
www.securin.io/zero-days/cve-2026-... WEB
https://www.securin.io/zero-days/cve-2026-44040-libc-rand-weak-rng-vnc-auth-challenge-ultravnc

Frequently Asked Questions

What is CVE-2026-44040?
CVE-2026-44040 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG).
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-44040?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-44040?
CVE-2026-44040 has a CVSS v3.1 base score of 4.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2026-44040?
CVE-2026-44040 is classified under CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.).
How can I check Maven dependencies for CVE-2026-44040?
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-j37g-g7hg-vhg6",
  "modified" : "2026-07-09T06:31:59Z",
  "published" : "2026-07-01T06:31:33Z",
  "aliases" : [ "CVE-2026-44040" ],
  "details" : "UltraVNC through 1.8.2.2 uses a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes() function seeds libc rand() with time(0) + getpid() + rand() and generates a 16-byte challenge. The combined seed space is approximately 31 bits (libc rand() internal state) and is entirely determined by publicly-observable values (wall-clock time and process ID). An attacker who can observe the authentication exchange can enumerate the seed space and predict the challenge within seconds, enabling forgery or offline brute-forcing of responses. Note: on Windows, the active code path may use vncEncryptBytes2.cpp which calls CryptGenRandom; reachability on shipped Windows binaries requires compile-graph verification and is under investigation.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44040"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ultravnc/UltraVNC"
  }, {
    "type" : "WEB",
    "url" : "https://uvnc.com"
  }, {
    "type" : "WEB",
    "url" : "https://www.securin.io/zero-days/cve-2026-44040-libc-rand-weak-rng-vnc-auth-challenge-ultravnc"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-338" ],
    "severity" : "MODERATE",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-01T05:16:20Z"
  }
}