Net::SAML2 versions before 0.86 for Perl allow authentication bypass because _verify_encrypted_assertion accepts an EncryptedAssertion whose decrypted content carries no signature
Summary
| CVE | CVE-2026-18108 |
|---|---|
| State | PUBLISHED |
| Assigner | CPANSec |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-03 14:16:25 UTC |
| Updated | 2026-08-06 18:37:01 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 9.8 CRITICAL from ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.002200000 probability, percentile 0.125830000 (date 2026-08-05)
Problem Types: CWE-347 | CWE-347 CWE-347 Improper Verification of Cryptographic Signature
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | DECLARED | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | Secondary | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/perl-net-saml2/perl-Net-SAML2/commit/d916468586404518b8cf3c78... | 9b29abf9-4ab0-4765-b253-1875cd9b441e | github.com | Patch |
| metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol... | 9b29abf9-4ab0-4765-b253-1875cd9b441e | metacpan.org | Product |
| metacpan.org/release/TIMLEGGE/Net-SAML2-0.86/changes | 9b29abf9-4ab0-4765-b253-1875cd9b441e | metacpan.org | Release Notes |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
Additional Advisory Data
Solutions
CNA: Upgrade to Net::SAML2 0.86 or later, which refuses to extract assertion content unless a signature covering the assertion chains to the configured trust anchor.
Workarounds
CNA: For deployments that cannot upgrade to 0.86, do not configure a decryption key_file, so EncryptedAssertions are never decrypted and consumed.
There are currently no legacy QID mappings associated with this CVE.