CVE-2020-36563Network attack vector

SAML signature forgery via hard-coded SHA-1

Published Dec 27, 2022 · Updated Apr 11, 2025

Weak hashing in Robots & Pencils go-saml allows remote attackers to forge XML signatures by causing controlled SHA-1 collisions. NewAuthnRequest and NewSignedResponse hard-code rsa-sha1 for SignatureMethod and sha1 for DigestMethod; validation also accepts SHA-1. Exploitation requires enough control over signed input to construct a collision, and successful forgery compromises SAML message integrity.

CVSS severity5.3
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak hashing in Robots & Pencils go-saml allows remote attackers to forge XML signatures by causing controlled SHA-1 collisions. NewAuthnRequest and NewSignedResponse hard-code rsa-sha1 for SignatureMethod and sha1 for DigestMethod; validation also accepts SHA-1. Exploitation requires enough control over signed input to construct a collision, and successful forgery compromises SAML message integrity.

The record

CVE
CVE-2020-36563
Published
Dec 27, 2022
Updated
Apr 11, 2025
Vendor
Robots & Pencils
Product
go-saml
Classifications
CWE-347, CWE-328
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 27, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 11, 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?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Robots & Pencils · go-samlAffected versions are unavailable in this record.

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-328Use of Weak Hash

Public exploit references

No public exploit references are available in this record.

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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