CVE-2026-18108: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-g48m-j5m7-625h
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CVSS 9.8
CWE-347
Published
Advisory Summary

CVE-2026-18108 is a CRITICAL (CVSS 9.8) security vulnerability vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product does not verify, or incorrectly verifies, the cryptographic signature for data.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-18108 at a Glance

CVE Identifier CVE-2026-18108
GHSA Identifier GHSA-g48m-j5m7-625h
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.8

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:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
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-2026-18108

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-2026-18108, 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-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. 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

Net::SAML2 versions before 0.86 for Perl allow authentication bypass because _verify_encrypted_assertion accepts an EncryptedAssertion whose decrypted content carries no signature. _verify_encrypted_assertion decrypts the EncryptedAssertion and returns it as verified when it carries no signature, via "return $xml unless $xpath->exists('dsig:Signature', $assert);". The signature check and the trust anchor check that follow run only when a signature is present, so a decrypted assertion with no dsig:Signature element reaches new_from_xml unverified and its NameID and attributes are read into the assertion object. An SP's encryption certificate is published in its SAML metadata so the IdP can encrypt to it, so any party can encrypt an unsigned assertion to that certificate, wrap it in a samlp:Response, and post it to the assertion consumer service. Any caller that configures a decryption key_file, and so accepts EncryptedAssertions, takes identity fields from an assertion that no trust anchor covers, and an unauthenticated party can authenticate as an arbitrary user. Callers with no key_file configured do not decrypt and are unaffected.

References

NVD — CVE-2026-18108 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-18108
Security Fix Commit FIX COMMIT
https://github.com/perl-net-saml2/perl-Net-SAML2/commit/d916468586404518b8cf3c78dbd001cc1f1046a7.patch
metacpan.org/release/timlegge/ne... WEB
https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L78
metacpan.org/release/timlegge/ne... WEB
https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.86/changes

Frequently Asked Questions

What is CVE-2026-18108?
CVE-2026-18108 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-347: Improper Verification of Cryptographic Signature.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-18108?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-18108?
CVE-2026-18108 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-18108?
CVE-2026-18108 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check Maven dependencies for CVE-2026-18108?
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-g48m-j5m7-625h",
  "modified" : "2026-08-03T21:31:35Z",
  "published" : "2026-08-03T15:32:47Z",
  "aliases" : [ "CVE-2026-18108" ],
  "details" : "Net::SAML2 versions before 0.86 for Perl allow authentication bypass because _verify_encrypted_assertion accepts an EncryptedAssertion whose decrypted content carries no signature.\n\n_verify_encrypted_assertion decrypts the EncryptedAssertion and returns it as verified when it carries no signature, via \"return $xml unless $xpath->exists('dsig:Signature', $assert);\". The signature check and the trust anchor check that follow run only when a signature is present, so a decrypted assertion with no dsig:Signature element reaches new_from_xml unverified and its NameID and attributes are read into the assertion object. An SP's encryption certificate is published in its SAML metadata so the IdP can encrypt to it, so any party can encrypt an unsigned assertion to that certificate, wrap it in a samlp:Response, and post it to the assertion consumer service.\n\nAny caller that configures a decryption key_file, and so accepts EncryptedAssertions, takes identity fields from an assertion that no trust anchor covers, and an unauthenticated party can authenticate as an arbitrary user. Callers with no key_file configured do not decrypt and are unaffected.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-18108"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/perl-net-saml2/perl-Net-SAML2/commit/d916468586404518b8cf3c78dbd001cc1f1046a7.patch"
  }, {
    "type" : "WEB",
    "url" : "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L78"
  }, {
    "type" : "WEB",
    "url" : "https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.86/changes"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-08-03T14:16:25Z"
  }
}