Critical Vulnerability in PHP Packages: Denial of Service Risk
Summary
UBUNTU-CVE-2017-8923: The zend_string_extend function in Zend/zend_string.h in PHP through 7.1.5 does not prevent changes to string objects that result in a negative length, which allows remote attackers to cause a denial of service (applicat... Affects php5 versions 5.5.3+dfsg-1ubuntu2 – 5.5.9+dfsg-1ubuntu4.9. No fix is published. How to fix ↓
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Background
PHP is a widely-used open-source scripting language designed for web development but also used as a general-purpose programming language. It is known for its ease of use, flexibility, and strong community support. The affected packages include various versions of PHP (5, 7.0, 7.2, 7.4) that are integral for running dynamic web applications. This vulnerability allows attackers to exploit string manipulation functions, leading to potential application crashes.
Vulnerability Detail
The zend_string_extend function in Zend/zend_string.h in PHP through 7.1.5 does not prevent changes to string objects that result in a negative length. This flaw can be exploited by remote attackers to cause a denial of service (application crash) or potentially have unspecified other impacts by leveraging a script's use of string concatenation with long strings. The vulnerability has a CVSS score of 9.8, indicating a critical level of severity.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
If immediate patching is not feasible, consider implementing input validation to restrict the length of strings processed by your PHP applications. This can help mitigate the risk of triggering the vulnerability until a proper update can be applied.
Conclusion
This report highlights a critical vulnerability in various PHP packages that can lead to denial of service attacks. It is crucial for users to update their PHP installations to the latest patched versions to mitigate risks. Additionally, implementing input validation can serve as a temporary workaround until updates are applied.
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FAQ
The vulnerability allows for denial of service attacks due to improper handling of string lengths in PHP.
PHP versions 5.5.9, 7.0.33, 7.2.24, and 7.4.3 are among those impacted by this vulnerability.
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Exploitation of this vulnerability can lead to application crashes and potentially allow attackers to execute further malicious actions.
Yes, Vulert can monitor and alert you in real-time for open-source vulnerabilities using just a manifest file like package-lock.json.
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