CVE-2026-7830: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-gf4x-6rw3-q4x6
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CVSS 7.4
CWE-326
Published
Advisory Summary

CVE-2026-7830 is a HIGH (CVSS 7.4) security vulnerability vulnerability (CWE-326: Inadequate Encryption Strength) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-7830 at a Glance

CVE Identifier CVE-2026-7830
GHSA Identifier GHSA-gf4x-6rw3-q4x6
Severity HIGH
CVSS v3.1 Base Score 7.4
CWE Classification CWE-326: Inadequate Encryption Strength
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.4

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: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 High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-7830

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-2026-7830, 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-326: Inadequate Encryption Strength, where the product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required. 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 inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNC_MsLogonIIAuth). In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer (DH_MAX_BITS controls the prime size). A 64-bit DH key can be broken by Pollard's rho algorithm in under one second on current hardware. Additionally, the private exponent is generated by the rng() function, which multiplies three libc rand() values seeded from time(NULL). With approximately 31 bits of internal state and a time-based seed, the private exponent is recoverable in under a minute by a passive observer. A network attacker who can observe the MS-Logon II handshake (via sniffing, recording, or man-in-the-middle) can derive the shared DH key and decrypt the encapsulated username and password, resulting in full credential disclosure. This affects legacy MS-Logon II connections; MS-Logon III (X25519 + AES-256-GCM) is unaffected.

References

NVD — CVE-2026-7830 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-7830
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-2026-7830-31-bit-dh-weak-rng-ms-logon-credential-interception-ultravnc

Frequently Asked Questions

What is CVE-2026-7830?
CVE-2026-7830 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-326: Inadequate Encryption Strength.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-7830?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-7830?
CVE-2026-7830 has a CVSS v3.1 base score of 7.4 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-7830?
CVE-2026-7830 is classified under CWE-326: Inadequate Encryption Strength (The product stores or transmits sensitive data using an encryption scheme that is theoretically sound, but is not strong enough for the level of protection required.).
How can I check Maven dependencies for CVE-2026-7830?
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-gf4x-6rw3-q4x6",
  "modified" : "2026-07-09T06:31:59Z",
  "published" : "2026-07-01T06:31:34Z",
  "aliases" : [ "CVE-2026-7830" ],
  "details" : "UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNC_MsLogonIIAuth). In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer (DH_MAX_BITS controls the prime size). A 64-bit DH key can be broken by Pollard's rho algorithm in under one second on current hardware. Additionally, the private exponent is generated by the rng() function, which multiplies three libc rand() values seeded from time(NULL). With approximately 31 bits of internal state and a time-based seed, the private exponent is recoverable in under a minute by a passive observer. A network attacker who can observe the MS-Logon II handshake (via sniffing, recording, or man-in-the-middle) can derive the shared DH key and decrypt the encapsulated username and password, resulting in full credential disclosure. This affects legacy MS-Logon II connections; MS-Logon III (X25519 + AES-256-GCM) is unaffected.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-7830"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ultravnc/UltraVNC"
  }, {
    "type" : "WEB",
    "url" : "https://uvnc.com"
  }, {
    "type" : "WEB",
    "url" : "https://www.securin.io/zero-days/cve-2026-7830-31-bit-dh-weak-rng-ms-logon-credential-interception-ultravnc"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-326" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-01T05:16:24Z"
  }
}