CVE-2026-18108
Net::SAML2 versions before 0.86 for Perl allow authentication bypass because _verify_encrypted_assertion accepts an EncryptedAssertion whose decrypted content carries no signature
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.
INFO
Published Date :
Aug. 3, 2026, 2:16 p.m.
Last Modified :
Oct. 23, 2026, 9:10 p.m.
Remotely Exploit :
Yes !
Source :
9b29abf9-4ab0-4765-b253-1875cd9b441e
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Update Net::SAML2 to version 0.86 or later.
- Apply vendor patches when available.
- Review authentication configurations for compliance.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-18108.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-18108 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-18108
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-18108 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-18108 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 23, 2026
Action Type Old Value New Value Added Translation Title: Net::SAML2 de TIMLEGGE, Description: Las versiones de Net::SAML2 anteriores a la 0.86 para Perl permiten la omisión de autenticación porque _verify_encrypted_assertion acepta una EncryptedAssertion cuyo contenido descifrado no lleva firma. _verify_encrypted_assertion descifra la EncryptedAssertion y la devuelve como verificada cuando no lleva firma, a través de “return $xml unless $xpath -> exists(’dsig:Signature’, $assert);”. La comprobación de firma y la comprobación de anclaje de confianza que le siguen se ejecutan solo cuando hay una firma presente, por lo que una aserción descifrada sin un elemento dsig:Signature llega a new_from_xml sin verificar y su NameID y atributos se leen en el objeto de aserción. El certificado de cifrado de un SP se publica en sus metadatos SAML para que el IdP pueda cifrar a él, por lo que cualquier parte puede cifrar una aserción sin firmar a ese certificado, envolverla en una samlp:Response y publicarla en el servicio de consumidor de aserciones. Cualquier llamador que configure un archivo de clave de descifrado, y por lo tanto acepta EncryptedAssertions, toma campos de identidad de una aserción que ningún anclaje de confianza cubre, y una parte no autenticada puede autenticarse como un usuario arbitrario. Los llamadores sin un key_file configurado no descifran y no se ven afectados. -
Initial Analysis by [email protected]
Aug. 06, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:timlegge:net::saml2:*:*:*:*:*:perl:*:* versions up to (excluding) 0.86 Added Reference Type CPANSec: https://github.com/perl-net-saml2/perl-Net-SAML2/commit/d916468586404518b8cf3c78dbd001cc1f1046a7.patch Types: Patch Added Reference Type CPANSec: https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L78 Types: Product Added Reference Type CPANSec: https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.86/changes Types: Release Notes -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 03, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added SSVC {'id': 'CVE-2026-18108', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-03T19:57:16.653167Z'} -
New CVE Received by 9b29abf9-4ab0-4765-b253-1875cd9b441e
Aug. 03, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://github.com/perl-net-saml2/perl-Net-SAML2', 'vendor': 'TIMLEGGE', 'product': 'Net::SAML2', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '0.86', 'versionType': 'custom'}], 'packageName': 'Net-SAML2', 'programFiles': ['lib/Net/SAML2/Protocol/Assertion.pm'], 'collectionURL': 'https://cpan.org/modules', 'defaultStatus': 'unaffected', 'programRoutines': [{'name': 'Net::SAML2::Protocol::Assertion::_verify_encrypted_assertion'}, {'name': 'Net::SAML2::Protocol::Assertion::new_from_xml'}]}] Added 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. Added CWE CWE-347 Added Reference https://github.com/perl-net-saml2/perl-Net-SAML2/commit/d916468586404518b8cf3c78dbd001cc1f1046a7.patch Added Reference https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L78 Added Reference https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.86/changes