CVE-2026-18568
XML::Sig versions from 0.29 before 0.72 for Perl allow signature verification bypass because verify returns true when every signature was skipped before any cryptographic check
Published Aug 3, 2026
CVSS 3.1 · 7.5 High
EPSS < 1%
KEV · Not listed
Description
XML::Sig versions from 0.29 before 0.72 for Perl allow signature verification bypass because verify returns true when every signature was skipped before any cryptographic check.
verify in lib/XML/Sig.pm counts the `//dsig:Signature` elements into `$numsigs` and iterates over them, but two paths reach `next` before any digest or key check runs: a `SignedInfo/Reference/@URI` that resolves to no element while `$numsigs` is greater than 1, and, when `id_attr` is set, a reference that does not match the requested ID. The loop records nothing about what it checked, so when every signature takes one of those paths control reaches the unconditional `return 1` that ends verify. Two `Signature` elements whose Reference URI names an ID that no element carries is enough, as is one such element combined with `id_attr`.
Any caller that passes untrusted XML to verify can receive a true return for a document in which no digest and no signature value was checked; a `cert` or `cert_text` trust anchor does not change this, because no key check runs. Versions up to 0.28 use an XML::XPath based verify that has no such skip and are not affected.
verify in lib/XML/Sig.pm counts the `//dsig:Signature` elements into `$numsigs` and iterates over them, but two paths reach `next` before any digest or key check runs: a `SignedInfo/Reference/@URI` that resolves to no element while `$numsigs` is greater than 1, and, when `id_attr` is set, a reference that does not match the requested ID. The loop records nothing about what it checked, so when every signature takes one of those paths control reaches the unconditional `return 1` that ends verify. Two `Signature` elements whose Reference URI names an ID that no element carries is enough, as is one such element combined with `id_attr`.
Any caller that passes untrusted XML to verify can receive a true return for a document in which no digest and no signature value was checked; a `cert` or `cert_text` trust anchor does not change this, because no key check runs. Versions up to 0.28 use an XML::XPath based verify that has no such skip and are not affected.
Affected Products
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CVE record
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NVD configurations
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Red Hat packages
No data
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OpenCVE enrichment
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
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| TIMLEGGE | XML::Sig | unaffected |
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No data.
| Vendor | Product | Versions | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Timlegge | Xml::sig |
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Remediation
Vendor Solution
Upgrade to XML::Sig 0.72 or later, which returns false when no reference digest was checked and matched.
Tracking
Advisories
Metrics
No CVSS v4.0
Attack Vector Network
Attack Complexity Low
Privileges Required None
Scope Unchanged
Confidentiality Impact None
Integrity Impact High
Availability Impact None
User Interaction None
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.319% probability within 30 days)
Exploitation none
Automatable yes
Technical Impact partial
References
History
Aug 5, 2026 10:45 AM
First appearance in the feed. Affected vendors updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Timlegge
Timlegge xml::sig |
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| Vendors & Products |
Timlegge
Timlegge xml::sig |
Aug 3, 2026 8:30 PM
Scoring metrics updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
cvssV3_1
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Aug 3, 2026 3:30 PM
Description updated. Title updated. Weaknesses updated. Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Description | XML::Sig versions from 0.29 before 0.72 for Perl allow signature verification bypass because verify returns true when every signature was skipped before any cryptographic check. verify in lib/XML/Sig.pm counts the `//dsig:Signature` elements into `$numsigs` and iterates over them, but two paths reach `next` before any digest or key check runs: a `SignedInfo/Reference/@URI` that resolves to no element while `$numsigs` is greater than 1, and, when `id_attr` is set, a reference that does not match the requested ID. The loop records nothing about what it checked, so when every signature takes one of those paths control reaches the unconditional `return 1` that ends verify. Two `Signature` elements whose Reference URI names an ID that no element carries is enough, as is one such element combined with `id_attr`. Any caller that passes untrusted XML to verify can receive a true return for a document in which no digest and no signature value was checked; a `cert` or `cert_text` trust anchor does not change this, because no key check runs. Versions up to 0.28 use an XML::XPath based verify that has no such skip and are not affected. | |
| Title | XML::Sig versions from 0.29 before 0.72 for Perl allow signature verification bypass because verify returns true when every signature was skipped before any cryptographic check | |
| Weaknesses | CWE-347 | |
| References |
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Weaknesses
