Signature verification bypass via skipped cryptographic checks
Published Aug 3, 2026 · Updated Aug 3, 2026
Improper signature verification in XML::Sig 0.29 through 0.71 allows attackers to make forged XML pass verification. XML::Sig::verify skips unmatched Reference URIs before digest or key checks, then returns true when every Signature element follows a skip path. Any caller that verifies untrusted XML can therefore accept altered content without checking a digest or signature value, even when a trust certificate is supplied.
Summary
What happened
Improper signature verification in XML::Sig 0.29 through 0.71 allows attackers to make forged XML pass verification. XML::Sig::verify skips unmatched Reference URIs before digest or key checks, then returns true when every Signature element follows a skip path. Any caller that verifies untrusted XML can therefore accept altered content without checking a digest or signature value, even when a trust certificate is supplied.
The record
- CVE
- CVE-2026-18568
- Published
- Aug 3, 2026
- Updated
- Aug 3, 2026
- Vendor
- Timothy Legge
- Product
- XML::Sig
- Classifications
- CWE-347
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 3, 2026CVE publishedPublication date reported by the CVE source.
- Aug 3, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0.29 <0.72
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream forged-signature regression testproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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