CVE-2026-7831: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-38w7-mq68-3h8q
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CVSS 7.6
CWE-193
Published
Advisory Summary

CVE-2026-7831 is a HIGH (CVSS 7.6) security vulnerability vulnerability (CWE-193: Off-by-one Error) affecting Software libraries in the Maven ecosystem. The weakness occurs when a product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-7831 at a Glance

CVE Identifier CVE-2026-7831
GHSA Identifier GHSA-38w7-mq68-3h8q
Severity HIGH
CVSS v3.1 Base Score 7.6
CWE Classification CWE-193: Off-by-one Error
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.6

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

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

How to Fix CVE-2026-7831

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-2026-7831, 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-193: Off-by-one Error, where a product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value. 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 viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required.

References

NVD — CVE-2026-7831 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-7831
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-2026-7831-off-by-one-stack-overflow-viewer-namelength-ultravnc

Frequently Asked Questions

What is CVE-2026-7831?
CVE-2026-7831 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-193: Off-by-one Error.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-7831?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-7831?
CVE-2026-7831 has a CVSS v3.1 base score of 7.6 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H.
What CWE is associated with CVE-2026-7831?
CVE-2026-7831 is classified under CWE-193: Off-by-one Error (A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.).
How can I check Maven dependencies for CVE-2026-7831?
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-38w7-mq68-3h8q",
  "modified" : "2026-07-09T06:31:59Z",
  "published" : "2026-07-01T06:31:34Z",
  "aliases" : [ "CVE-2026-7831" ],
  "details" : "UltraVNC viewer through 1.8.2.2 contains an off-by-one stack buffer overflow in the RFB ServerInit message handler. In vncviewer/ClientConnection.cpp, when the server-supplied nameLength equals exactly 2024 the code declares a 2024-byte stack buffer _dn[2024] and calls ReadString(_dn, 2024). ReadString writes the NUL terminator at buf[length], i.e., _dn[2024], one byte past the end of the stack buffer. A malicious VNC server can trigger this condition by advertising a desktop name of length 2024 in its ServerInit message. On release builds without stack canaries the single-byte NUL overwrite adjacent stack data. On builds with /GS stack protection the canary is corrupted and the process terminates, resulting in denial of service. User interaction (connecting the viewer to the malicious server) is required.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-7831"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ultravnc/UltraVNC"
  }, {
    "type" : "WEB",
    "url" : "https://uvnc.com"
  }, {
    "type" : "WEB",
    "url" : "https://www.securin.io/zero-days/cve-2026-7831-off-by-one-stack-overflow-viewer-namelength-ultravnc"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-193" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-01T05:16:24Z"
  }
}