Buffer Overflow Vulnerability in Expat Package: CVE-2026-25210
Summary
ALPINE-CVE-2026-25210: In libexpat before 2.7.4, the doContent function does not properly determine the buffer size bufSize because there is no integer overflow check for tag buffer reallocation. Affects expat versions < 2.7.4-r0. Fixed in 2.7.4-r0. How to fix ↓
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Background
Expat is an XML parsing library widely used in various applications for its efficiency and ease of use. It provides a simple API for parsing XML documents and is known for its performance. However, like many libraries, it can be susceptible to vulnerabilities that may compromise the security of applications relying on it. The vulnerability identified as CVE-2026-25210 affects versions of Expat prior to 2.7.4, where improper buffer size determination can lead to potential exploitation.
Vulnerability Detail
The vulnerability arises from the doContent function in libexpat, which fails to properly check for integer overflow during tag buffer reallocation. This oversight can lead to a buffer overflow, allowing attackers to manipulate the buffer size and potentially execute arbitrary code. The ramifications of this vulnerability can be severe, including unauthorized access to system resources and data corruption, making it critical for users of affected versions to address this issue promptly.
How To Fix
Minimum fixed version
2.7.4-r0
This is the first release that contains the fix.
sudo apk add --upgrade expatTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If immediate updating is not feasible, a temporary workaround may involve restricting access to the application or implementing additional security measures to mitigate the risk of exploitation until the package can be updated.
Conclusion
CVE-2026-25210 presents a significant risk to applications using vulnerable versions of the Expat library. It is crucial for developers and system administrators to update to the fixed version 2.7.4-r0 or later to mitigate the risk of exploitation. Regular monitoring of open-source vulnerabilities, such as through tools like Vulert, can help maintain application security.
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FAQ
CVE-2026-25210 is a vulnerability in the Expat XML parsing library that can lead to buffer overflow due to improper buffer size checks.
Versions of Expat prior to 2.7.4 are affected by this vulnerability.
Exploitation of this vulnerability can lead to unauthorized access, data corruption, or arbitrary code execution.
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 CVSS score for CVE-2026-25210 is 6.9, indicating a medium severity level.
References
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