XML::Sig versions before 0.71 for Perl allow XPath injection in ID lookup.
verify() and _get_signed_xml() in lib/XML/Sig.pm build XPath expressions by concatenating the SignedInfo/Reference/@URI value read from the document being verified. The value is neither escaped nor checked against the NCName grammar that XML requires of an ID, so a URI containing a single quote closes the string literal in the generated expression and appends arbitrary XPath operators.
A crafted URI can make the lookup match elements the reference does not name, or every element in the document, so which node is selected for digest verification is decided by the injected expression rather than by the reference.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v3.1
Vulnerable Products 1
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Xml\ \
cpe:2.3:a:xml\:\:sig_project:xml\:\:sig:*:*:*:*:*:perl:*:*
|
— |
0.71
|
References 3
https://github.com/perl-net-saml2/perl-XML-Sig/commit/69ad2b421118fadd33d57f50b…
9b29abf9-4ab0-4765-b253-1875cd9b441e
https://github.com/perl-net-saml2/perl-XML-Sig/commit/a85aad21aa767ac1c158bbfc1…
9b29abf9-4ab0-4765-b253-1875cd9b441e
https://metacpan.org/release/TIMLEGGE/XML-Sig-0.71/changes
9b29abf9-4ab0-4765-b253-1875cd9b441e