CVE-2026-103603: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-gpr4-c479-xrw4
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CWE-789
Published
Advisory Summary

CVE-2026-103603 is a HIGH security vulnerability vulnerability (CWE-789: Memory Allocation with Excessive Size Value) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-103603 at a Glance

CVE Identifier CVE-2026-103603
GHSA Identifier GHSA-gpr4-c479-xrw4
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-789: Memory Allocation with Excessive Size Value
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

How to Fix CVE-2026-103603

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-2026-103603, 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-789: Memory Allocation with Excessive Size Value, where the product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. 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

Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker who can supply both an HSS public key and a signature to cause a denial of service through memory exhaustion via a public key encoding with an excessive level count, because the level count L read when parsing an HSS public key was not checked against the RFC 8554 maximum of 8, and signature parsing then allocated an array of L - 1 entries before reading any further signature data. A single verification can commit up to about 17 GB of memory or fail with an OutOfMemoryException.

References

NVD — CVE-2026-103603 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-103603
Security Fix Commit FIX COMMIT
https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7
GitHub Advisory / Wiki ADVISORY
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603

Frequently Asked Questions

What is CVE-2026-103603?
CVE-2026-103603 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-789: Memory Allocation with Excessive Size Value.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-103603?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What CWE is associated with CVE-2026-103603?
CVE-2026-103603 is classified under CWE-789: Memory Allocation with Excessive Size Value (The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.).
How can I check Maven dependencies for CVE-2026-103603?
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-gpr4-c479-xrw4",
  "modified" : "2026-10-02T09:31:19Z",
  "published" : "2026-10-02T09:31:19Z",
  "aliases" : [ "CVE-2026-103603" ],
  "details" : "Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker who can supply both an HSS public key and a signature to cause a denial of service through memory exhaustion via a public key encoding with an excessive level count, because the level count L read when parsing an HSS public key was not checked against the RFC 8554 maximum of 8, and signature parsing then allocated an array of L - 1 entries before reading any further signature data. A single verification can commit up to about 17 GB of memory or fail with an OutOfMemoryException.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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-2026-103603"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-789" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-10-02T08:17:00Z"
  }
}