CVE-2026-18089Network attack vector

Authentication bypass via response-embedded signing certificate

Published Aug 3, 2026 · Updated Aug 3, 2026

Improper certificate validation in Net::SAML2 before 0.86 allows remote attackers to authenticate with forged SAML responses. Net::SAML2::Role::VerifyXML validates the XML signature with the X.509 certificate embedded in the response, then returns successfully without checking a configured trust anchor. The bypass is reachable when Binding::POST or Assertion->new_from_xml is used without cacert, cert_text, or anchors, allowing an attacker-signed assertion to establish an arbitrary identity.

CVSS severity7.5
High
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Net::SAML2 before 0.86 allows remote attackers to authenticate with forged SAML responses. Net::SAML2::Role::VerifyXML validates the XML signature with the X.509 certificate embedded in the response, then returns successfully without checking a configured trust anchor. The bypass is reachable when Binding::POST or Assertion->new_from_xml is used without cacert, cert_text, or anchors, allowing an attacker-signed assertion to establish an arbitrary identity.

The record

CVE
CVE-2026-18089
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Timothy Legge
Product
Net::SAML2
Classifications
CWE-347, CWE-295, T1606.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2026CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=0 <0.86

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Timothy Legge · Net::SAML2version=0 <0.86

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
CWE-295Improper Certificate Validation
T1606.002Forge Web Credentials: SAML Tokens

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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