CVE-2026-72844: Software Security Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-4fhc-8rq3-cjvg
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CVSS 6.3
CWE-843
Published
Advisory Summary

CVE-2026-72844 is a MODERATE (CVSS 6.3) security vulnerability vulnerability (CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-72844 at a Glance

CVE Identifier CVE-2026-72844
GHSA Identifier GHSA-4fhc-8rq3-cjvg
Severity MODERATE
CVSS v3.1 Base Score 6.3
CWE Classification CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 6.3

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

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

How to Fix CVE-2026-72844

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-2026-72844, 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-843: Access of Resource Using Incompatible Type ('Type Confusion'), where the product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type. 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

The Lean 4 kernel does not verify that the structure named in a projection expression matches the type of the value being projected, and environment::add_inductive in src/kernel/inductive.cpp did not type check the nested inductive applications that are replaced by auxiliary types, so their parametric arguments escaped checking. A metaprogram running in the Lean process can register an ill-typed nested inductive whose constructor applies a .proj C 0 projection to a value of the unrelated type W, and the kernel admits the declaration through the ordinary checked addDecl path at maximum kernel checking, without sorry, unsafeCast, debug.skipKernelTC, addDeclWithoutChecking, FFI, or a modified .olean file. The result is a type confusion yielding a proof of False that carries no axioms, from which any proposition can be derived. The published proof of concept additionally pads two expressions until their hashes and approximate depths collide, which defeats kernel caching; that is the technique used to reach the flaw, not its cause. Exploitation requires running a metaprogram in-process, for example by building a project or importing a malicious Lake dependency.

References

NVD — CVE-2026-72844 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-72844
Software Source Repository REPOSITORY
https://github.com/leanprover/lean4/issues/14576
Software Source Repository REPOSITORY
https://github.com/leanprover/lean4/pull/14577
Security Fix Commit FIX COMMIT
https://github.com/leanprover/lean4/commit/a39eab69e1eee9ad38f4efe507907b1026a77808
Software Source Repository REPOSITORY
https://github.com/endrazine/lean-cve-poc
Software Source Repository REPOSITORY
https://github.com/leanprover/lean4
Software Source Repository REPOSITORY
https://github.com/xrchz/CollatzLean
Software Security Information SECURITY
https://www.openwall.com/lists/oss-security/2026/08/02/1
www.vulncheck.com/advisories/lean-4-k... WEB
https://www.vulncheck.com/advisories/lean-4-kernel-type-checking-bypass-via-mismatched-structure-projections

Frequently Asked Questions

What is CVE-2026-72844?
CVE-2026-72844 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-843: Access of Resource Using Incompatible Type ('Type Confusion').
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-72844?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-72844?
CVE-2026-72844 has a CVSS v3.1 base score of 6.3 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2026-72844?
CVE-2026-72844 is classified under CWE-843: Access of Resource Using Incompatible Type ('Type Confusion') (The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.).
How can I check Maven dependencies for CVE-2026-72844?
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 
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  "id" : "GHSA-4fhc-8rq3-cjvg",
  "modified" : "2026-08-20T18:31:00Z",
  "published" : "2026-08-20T18:31:00Z",
  "aliases" : [ "CVE-2026-72844" ],
  "details" : "The Lean 4 kernel does not verify that the structure named in a projection expression matches the type of the value being projected, and environment::add_inductive in src/kernel/inductive.cpp did not type check the nested inductive applications that are replaced by auxiliary types, so their parametric arguments escaped checking. A metaprogram running in the Lean process can register an ill-typed nested inductive whose constructor applies a .proj C 0 projection to a value of the unrelated type W, and the kernel admits the declaration through the ordinary checked addDecl path at maximum kernel checking, without sorry, unsafeCast, debug.skipKernelTC, addDeclWithoutChecking, FFI, or a modified .olean file. The result is a type confusion yielding a proof of False that carries no axioms, from which any proposition can be derived. The published proof of concept additionally pads two expressions until their hashes and approximate depths collide, which defeats kernel caching; that is the technique used to reach the flaw, not its cause. Exploitation requires running a metaprogram in-process, for example by building a project or importing a malicious Lake dependency.",
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  "database_specific" : {
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    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-08-20T18:16:45Z"
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