6.9

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2025-48995

CVE-2025-48995: 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.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2025-48995

CVE-2025-48995:

6.9

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
signxml	pip	< 4.0.4	4.0.4

Technical Details

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Miggo AI

Root Cause Analysis

The vulnerability described is a timing attack in the HMAC signature verification process of the SignXML library. The provided commit patch clearly shows the modification in the verify method within the signxml/verifier.py file. The vulnerable code was the direct comparison of the user-supplied hash with the calculated HMAC (raw_signature == signer.finalize()). This comparison is not time-constant, meaning the time it takes to execute can vary depending on how many bytes match, leaking information about the correct HMAC. The patch replaces this with signer.verify(raw_signature), which is designed to be a constant-time operation, preventing the timing leak. Therefore, the signxml.XMLVerifier.verify function is the direct location of the vulnerability when called with parameters that trigger HMAC verification.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

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WAF Protection Rules

WAF Rule

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Reasoning

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