Critical Memory Allocation Vulnerability in Expat Package
Summary
ALSA-2025:21030: Important: expat security update. Affects expat versions < 2.7.1-1.el10_1.3. Fixed in 2.7.1-1.el10_1.3. How to fix ↓
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Background
Expat is a widely used C library designed for parsing XML documents. It is known for its efficiency and flexibility, making it a popular choice among developers for handling XML data. However, it has recently been identified that the library is susceptible to a security flaw that can lead to excessive memory allocation, potentially compromising system stability and security.
Vulnerability Detail
The vulnerability, identified as CVE-2025-59375, allows attackers to exploit the libexpat component of Expat by submitting a small XML document that triggers large dynamic memory allocations. This can lead to Denial of Service (DoS) conditions or other malicious activities, as the system may become overwhelmed by the unexpected memory usage. The issue arises from improper handling of certain XML parsing scenarios, making it critical for users to address this vulnerability promptly.
How To Fix
Minimum fixed version
2.7.1-1.el10_1.3
This is the first release that contains the fix.
sudo dnf update expatTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can limit the size of XML documents being processed or implement additional validation checks before parsing to mitigate the risk of triggering the vulnerability. However, this is not a substitute for applying the official patch.
Conclusion
The Expat library has a critical vulnerability that can lead to significant security risks if not addressed. Users are strongly advised to update to the latest patched version to ensure their systems remain secure. For ongoing monitoring of open-source vulnerabilities, consider using Vulert, which can alert you in real-time without requiring code access.
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FAQ
CVE-2025-59375 is a security vulnerability in the Expat library that allows attackers to cause large memory allocations through specially crafted XML documents.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
The vulnerability can lead to Denial of Service (DoS) conditions, system instability, and potential exploitation by attackers to compromise system security.
Yes, a patch is available in version 2.7.1-1.el10_1.3 of the Expat package. Users are encouraged to update to this version.
If immediate updates are not possible, consider implementing input validation to limit the size of XML documents processed as a temporary measure.
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