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CVE-2025-48995— SignXML's signature verification with HMAC is vulnerable to a timing attack

Quick assessment

Affected
XML-Security signxml
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

SignXML是XML-Security开源的一个Python XML签名和XAdES库。 SignXML 4.0.4之前版本存在安全漏洞，该漏洞源于时序攻击缺陷，可能导致HMAC密钥泄露。

AI Predicted 5.9 Difficulty: Hard EPSS 0.21% · P12

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle
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I. Basic Information for CVE-2025-48995

Vulnerability Information
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Vulnerability Title
SignXML's signature verification with HMAC is vulnerable to a timing attack
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
通过时间差异性导致的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
SignXML 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SignXML是XML-Security开源的一个Python XML签名和XAdES库。 SignXML 4.0.4之前版本存在安全漏洞，该漏洞源于时序攻击缺陷，可能导致HMAC密钥泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
XML-Security signxml < 4.0.4 -

II. Public POCs for CVE-2025-48995

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III. Intelligence Information for CVE-2025-48995

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IV. Related Vulnerabilities

Same product: signxml
Same vendor: XML-Security
Same weakness: CWE-208

V. Comments for CVE-2025-48995

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