CVE-2025-48995
SignXML's signature verification with HMAC is vulnerable to a timing attack
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
6.9
SignXML's signature verification with HMAC is vulnerable to a timing attack
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
CVE-2025-48995- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Weakness
- CWE-208
- Updated
- 2026-11-02
EUVDEUVD-2025-16676
6.9
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
EUVD-2025-16676- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-gmhf-gg8w-jw42
6.9
SignXML's signature verification with HMAC is vulnerable to a timing attack
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 timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
GHSA-gmhf-gg8w-jw42- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Weakness
- CWE-208
- Updated
- 2026-11-02
NVD
6.9
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
CVE-2025-48995- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Weakness
- CWE-208
- Updated
- 2026-11-02
OSV
6.9
SignXML's signature verification with HMAC is vulnerable to a timing attack
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
CVE-2025-48995- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Weakness
- CWE-208
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2025-48995
6.9
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
DEBIAN-CVE-2025-48995- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Updated
- 2026-11-02
OSVGHSA-gmhf-gg8w-jw42
6.9
SignXML's signature verification with HMAC is vulnerable to a timing attack
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 timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
GHSA-gmhf-gg8w-jw42- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Weakness
- CWE-208
- Updated
- 2026-11-02
OSVPYSEC-2026-1922
6.9
SignXML's signature verification with HMAC is vulnerable to a timing attack
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 timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
PYSEC-2026-1922- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2025-48995
6.9
SignXML is an implementation of the W3C XML Signature standard in Python. When verifying signatures with X509 certificate validation turned off and HMAC shared secret set (signxml.XMLVerifier.verify(require_x509=False, hmac_key=...), versions of SignXML prior to 4.0.4 are vulnerable to a potential timing attack. The verifier may leak information about the correct HMAC when comparing it with the user supplied hash, allowing users to reconstruct the correct HMAC for any data.
- Record
UBUNTU-CVE-2025-48995- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
signxmlPyPI |
before 4.0.4 | 4.0.4 |
python-signxmlDebian:13 |
before 4.0.5+dfsg-1 | 4.0.5+dfsg-1 |
python-signxmlDebian:14 |
before 4.0.5+dfsg-1 | 4.0.5+dfsg-1 |
signxmlPyPI |
before 4.0.4, plus listed versions 0.0.10.1.00.1.10.1.20.1.3 Show 45 moreShow less0.1.40.1.50.1.60.1.70.1.80.1.90.2.00.2.10.2.20.2.30.2.40.2.50.2.60.2.70.2.80.2.90.3.00.3.10.3.20.3.30.3.40.3.50.3.60.3.70.3.80.3.90.4.00.4.10.4.20.4.30.4.40.4.50.4.60.5.00.6.01.0.01.0.11.0.22.0.02.1.42.10.02.10.12.2.02.2.12.2.2 |
4.0.4 |
python-signxmlUbuntu:25.10 |
All versions, plus listed versions 4.0.3+dfsg-14.0.5+dfsg-14.0.5+dfsg-2 |
None known |
python-signxmlUbuntu:26.10 |
All versions, plus listed versions 4.2.0+dfsg-14.4.0+dfsg-1 |
None known |
python-signxmlUbuntu:26.04:LTS |
All versions, plus listed versions 4.0.5+dfsg-24.2.0+dfsg-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-48995 is a medium vulnerability (CVSS 6.9) in Xml-security Signxml, published June 2, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.24%, the 15th percentile. Fixed in signxml 4.0.4.
References
github.com/XML-Security/signxml/security/advisories/GHSA-gmhf-gg8w-jw42
github.com/XML-Security/signxml/commit/1b501faaacf34cf978a52dbc6915ec11e27611cd
nvd.nist.gov/vuln/detail/CVE-2025-48995
github.com/advisories/GHSA-gmhf-gg8w-jw42
github.com/CVEProject/cvelistV5/tree/main/cves/2025/48xxx/CVE-2025-48995.json
security-tracker.debian.org/tracker/CVE-2025-48995
Left out here: 27 versions. The JSON record has them.