Critical Memory Allocation Vulnerability in Expat XML Parsing Library
Summary
ALSA-2025:21776: Important: expat security update. Affects expat versions < 2.5.0-1.el8_10. Fixed in 2.5.0-1.el8_10. How to fix ↓
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Background
Expat is a widely-used C library designed for parsing XML documents efficiently. It is known for its speed and flexibility, making it a popular choice for software developers working with XML data. However, it has been identified that certain versions of Expat are vulnerable to a security issue that allows attackers to exploit memory allocation processes, potentially leading to denial of service or other malicious activities.
Vulnerability Detail
The vulnerability, identified as CVE-2025-59375, arises from the libexpat component of the Expat library. Attackers can trigger large dynamic memory allocations by submitting a small XML document for parsing. This can lead to excessive memory consumption, resulting in application crashes or degraded performance. The issue is particularly concerning as it can be exploited with minimal input, making it a low-barrier attack vector for malicious actors.
How To Fix
Minimum fixed version
2.5.0-1.el8_10
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 measure, users can limit the size of XML documents that are parsed by the Expat library. This can be done by implementing checks in the application code to reject documents that exceed a certain size threshold, thus mitigating the risk of memory allocation attacks.
Conclusion
The Expat XML parsing library has a critical vulnerability that can be exploited through memory allocation attacks. It is crucial for users to update to the latest patched version to safeguard their applications. Implementing temporary workarounds can help mitigate risks until the update is applied.
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FAQ
CVE-2025-59375 is a security vulnerability in the Expat XML parsing library that allows attackers to exploit memory allocation processes through small XML documents.
You can use Vulert's 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, application crashes, or performance degradation due to excessive memory consumption.
Yes, a patch is available in version 2.5.0-1.el8_10 of the Expat library. Users should update to this version or later.
If an immediate update is not possible, implement size checks on XML documents being parsed to limit the risk of exploitation.
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