CVE-2026-39923: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-3mr9-883x-4f3x
Share
CVSS 8.1
CWE-324
Published
Advisory Summary

CVE-2026-39923 is a CRITICAL (CVSS 8.1) security vulnerability vulnerability (CWE-324: Use of a Key Past its Expiration Date) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product uses a cryptographic key or password past its expiration date, which diminishes its safety significantly by increasing the timing window for cracking attacks against that key.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-39923 at a Glance

CVE Identifier CVE-2026-39923
GHSA Identifier GHSA-3mr9-883x-4f3x
Severity CRITICAL
CVSS v3.1 Base Score 8.1
CWE Classification CWE-324: Use of a Key Past its Expiration Date
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-2026-39923

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-2026-39923, 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-324: Use of a Key Past its Expiration Date, where the product uses a cryptographic key or password past its expiration date, which diminishes its safety significantly by increasing the timing window for cracking attacks against that key. 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

Flarum before 1.8.16 contains a password reset token expiry bypass vulnerability that allows unauthenticated attackers to reuse expired password reset tokens by submitting them directly to the reset processing endpoint. The SavePasswordController::handle() method calls PasswordToken::findOrFail() without performing any expiry validation, allowing attackers to bypass the 24-hour token lifetime enforced only during form rendering and change any account's password to gain an authenticated session.

References

NVD — CVE-2026-39923 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39923
Software Source Repository REPOSITORY
https://github.com/flarum/framework/pull/4545
Security Fix Commit FIX COMMIT
https://github.com/flarum/framework/commit/2803058d0f9dc38252326070b46d4484fe5a857d
Software Release RELEASE
https://github.com/flarum/framework/releases/tag/v1.8.16
www.vulncheck.com/advisories/flarum-p... WEB
https://www.vulncheck.com/advisories/flarum-password-reset-token-expiry-bypass-via-post-reset

Frequently Asked Questions

What is CVE-2026-39923?
CVE-2026-39923 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-324: Use of a Key Past its Expiration Date.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-39923?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-39923?
CVE-2026-39923 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-2026-39923?
CVE-2026-39923 is classified under CWE-324: Use of a Key Past its Expiration Date (The product uses a cryptographic key or password past its expiration date, which diminishes its safety significantly by increasing the timing window for cracking attacks against that key.).
How can I check Maven dependencies for CVE-2026-39923?
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-3mr9-883x-4f3x",
  "modified" : "2026-08-05T18:31:35Z",
  "published" : "2026-08-05T18:31:35Z",
  "aliases" : [ "CVE-2026-39923" ],
  "details" : "Flarum before 1.8.16 contains a password reset token expiry bypass vulnerability that allows unauthenticated attackers to reuse expired password reset tokens by submitting them directly to the reset processing endpoint. The SavePasswordController::handle() method calls PasswordToken::findOrFail() without performing any expiry validation, allowing attackers to bypass the 24-hour token lifetime enforced only during form rendering and change any account's password to gain an authenticated session.",
  "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:H/AT:N/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-2026-39923"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flarum/framework/pull/4545"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flarum/framework/commit/2803058d0f9dc38252326070b46d4484fe5a857d"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flarum/framework/releases/tag/v1.8.16"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/flarum-password-reset-token-expiry-bypass-via-post-reset"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-324" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-08-05T16:16:55Z"
  }
}