PYSEC-2026-1921

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Import Source
https://github.com/pypa/advisory-database/blob/main/vulns/signxml/PYSEC-2026-1921.yaml
JSON Data
https://api.osv.dev/v1/vulns/PYSEC-2026-1921
Aliases
Published
2026-07-07T16:02:53.867049Z
Modified
2026-07-07T17:48:12.634281520Z
Severity
  • 6.9 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N CVSS Calculator
Summary
SignXML's signature verification with HMAC is vulnerable to an algorithm confusion attack
Details

When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), prior versions of SignXML are vulnerable to a potential algorithm confusion attack. Unless the user explicitly limits the expected signature algorithms using the signxml.XMLVerifier.verify(expect_config=...) setting, an attacker may supply a signature unexpectedly signed with a key other than the provided HMAC key, using a different (asymmetric key) signature algorithm.

Starting with signxml 4.0.4, specifying hmac_key causes the set of accepted signature algorithms to be restricted to HMAC only, if not already restricted by the user.

References

Affected packages

PyPI / signxml

Package

Name
signxml
View open source insights on deps.dev
Purl
pkg:pypi/signxml

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
4.0.4

Affected versions

0.*
0.0.1
0.1.0
0.1.1
0.1.2
0.1.3
0.1.4
0.1.5
0.1.6
0.1.7
0.1.8
0.1.9
0.2.0
0.2.1
0.2.2
0.2.3
0.2.4
0.2.5
0.2.6
0.2.7
0.2.8
0.2.9
0.3.0
0.3.1
0.3.2
0.3.3
0.3.4
0.3.5
0.3.6
0.3.7
0.3.8
0.3.9
0.4.0
0.4.1
0.4.2
0.4.3
0.4.4
0.4.5
0.4.6
0.5.0
0.6.0
1.*
1.0.0
1.0.1
1.0.2
2.*
2.0.0
2.1.4
2.2.0
2.2.1
2.2.2
2.2.3
2.2.4
2.2.6
2.3.0
2.4.0
2.5.2
2.6.0
2.7.0
2.7.1
2.7.2
2.7.3
2.8.0
2.8.1
2.8.2
2.9.0
2.10.0
2.10.1
3.*
3.0.0
3.0.1
3.0.2
3.1.0
3.1.1
3.2.0
3.2.1
3.2.2
4.*
4.0.0
4.0.1
4.0.2
4.0.3

Database specific

source 
"https://github.com/pypa/advisory-database/blob/main/vulns/signxml/PYSEC-2026-1921.yaml"