Denial of Service Vulnerability in Python 2.7: Hash Collision Exploit
Summary
UBUNTU-CVE-2013-7040: Python 2.7 before 3.4 only uses the last eight bits of the prefix to randomize hash values, which causes it to compute hash values without restricting the ability to trigger hash collisions predictably and makes it easie... Affects python2.7 versions 2.7.5-8ubuntu3 – 2.7.6-8ubuntu0.6+esm9. No fix is published. How to fix ↓
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Background
Python 2.7 is a widely-used programming language known for its simplicity and versatility. It is utilized in various applications ranging from web development to data analysis. However, a vulnerability exists in its hash table implementation, which can lead to denial of service attacks when exploited. This issue arises from the way Python 2.7 handles hash values, specifically using only the last eight bits of the prefix for randomization, making it susceptible to hash collisions.
Vulnerability Detail
Python 2.7 before version 3.4 has a vulnerability that allows attackers to trigger hash collisions predictably. This occurs due to an incomplete fix for CVE-2012-1150, where the hash values are computed without sufficient randomness. As a result, attackers can craft specific inputs that lead to excessive CPU consumption, causing denial of service in applications that rely on hash tables. This vulnerability poses a significant risk, especially in context-dependent scenarios where an attacker can control the input.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, avoid using hash tables with untrusted input or implement input validation to mitigate the risk of hash collision attacks. Additionally, consider using alternative data structures that are less susceptible to such vulnerabilities.
Conclusion
The vulnerability in Python 2.7, identified as CVE-2013-7040, poses a significant risk of denial of service due to predictable hash collisions. It is crucial for users to upgrade to a patched version of Python or implement workarounds to mitigate this risk. Regular monitoring and vulnerability assessment using tools like Vulert can help maintain application security.
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FAQ
CVE-2013-7040 is a vulnerability in Python 2.7 that allows attackers to exploit hash collisions, leading to potential denial of service.
You can check if your application is affected by using Vulert, which monitors open-source vulnerabilities in real-time. Visit Vulert Scanner to analyze your manifest file.
The primary risk is denial of service, where an attacker can cause excessive CPU usage by exploiting hash collisions, potentially leading to application downtime.
Yes, the recommended fix is to upgrade to Python 3.4 or later, which includes necessary patches for this vulnerability.
If upgrading is not feasible, implement input validation or avoid using hash tables with untrusted input as a temporary workaround.
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