CVE-2025-40934Public exploitNetwork attack vector

Authentication bypass via unsigned XML acceptance

Published Nov 26, 2025 · Updated Nov 28, 2025

Improper signature verification in XML::Sig 0.27 through 0.67 allows remote attackers to bypass XML trust checks with unsigned documents. The verify() routine returns true when an XML document contains no Signature node, treating the absence of a failed check as success. Any application that trusts this result can accept attacker-modified XML after its signature is removed, including SAML authentication data.

CVSS severity9.3
Critical
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper signature verification in XML::Sig 0.27 through 0.67 allows remote attackers to bypass XML trust checks with unsigned documents. The verify() routine returns true when an XML document contains no Signature node, treating the absence of a failed check as success. Any application that trusts this result can accept attacker-modified XML after its signature is removed, including SAML authentication data.

The record

CVE
CVE-2025-40934
Published
Nov 26, 2025
Updated
Nov 28, 2025
Vendor
Timothy Legge
Product
XML::Sig
Classifications
CWE-347, CAPEC-115, T1606.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 26, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 28, 2025Record 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.

  1. Affected versionversion=0.27 <0.68

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Timothy Legge · XML::Sigversion=0.27 <0.68

Published CVSS scores

9.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
CAPEC-115Authentication Bypass
T1606.002Forge Web Credentials: SAML Tokens

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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