========================================================================
CVE-2026-18108                                       CPAN Security Group
========================================================================

         CVE ID:  CVE-2026-18108
   Distribution:  Net-SAML2
       Versions:  before 0.86

       MetaCPAN:  https://metacpan.org/dist/Net-SAML2
       VCS Repo:  https://github.com/perl-net-saml2/perl-Net-SAML2

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.

Problem types
-------------
- CWE-347 Improper Verification of Cryptographic Signature

Workarounds
-----------
For deployments that cannot upgrade to 0.86, do not configure a
decryption key_file, so EncryptedAssertions are never decrypted and
consumed.

Solutions
---------
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.

References
----------
https://github.com/perl-net-saml2/perl-Net-SAML2/commit/d916468586404518b8cf3c78dbd001cc1f1046a7.patch
https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.86/changes
https://metacpan.org/release/TIMLEGGE/Net-SAML2-0.85/source/lib/Net/SAML2/Protocol/Assertion.pm#L78