CVE-2017-11144 in PHP
Summary
by MITRE
In PHP before 5.6.31, 7.x before 7.0.21, and 7.1.x before 7.1.7, the openssl extension PEM sealing code did not check the return value of the OpenSSL sealing function, which could lead to a crash of the PHP interpreter, related to an interpretation conflict for a negative number in ext/openssl/openssl.c, and an OpenSSL documentation omission.
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Analysis
by VulDB Data Team • 12/12/2022
The vulnerability identified as CVE-2017-11144 represents a critical flaw in PHP's openssl extension that affects multiple versions of the PHP runtime environment. This issue specifically impacts PHP versions prior to 5.6.31, 7.0.21, and 7.1.7, creating a significant security risk for systems utilizing PHP applications that rely on OpenSSL functionality for encryption operations. The flaw manifests within the PEM sealing code implementation where proper error handling mechanisms are absent, potentially leading to interpreter crashes and service disruptions.
The technical root cause of this vulnerability lies in the improper handling of return values from OpenSSL sealing functions within the ext/openssl/openssl.c source file. When the OpenSSL sealing process encounters certain conditions, it may return negative values that indicate errors or exceptional states. However, PHP's implementation fails to properly validate these return codes before proceeding with subsequent operations. This interpretation conflict for negative numbers creates a scenario where the PHP interpreter encounters unexpected values that trigger abrupt termination or memory corruption, effectively causing a denial of service condition. The vulnerability stems from a documentation omission in the underlying OpenSSL library that does not clearly specify the expected behavior of sealing functions under all operational conditions.
From an operational impact perspective, this vulnerability exposes systems to potential denial of service attacks where malicious actors could craft specific inputs to trigger the crash condition in PHP interpreters. The vulnerability is particularly concerning because it affects widely used PHP versions and could impact web applications that utilize OpenSSL for secure communications, certificate handling, or data encryption. When exploited, the vulnerability results in complete interpreter crashes, requiring system administrators to restart services and potentially leading to extended downtime for affected applications. The crash condition affects not only individual PHP processes but can also impact entire web server instances, making it a significant concern for enterprise environments and cloud deployments where availability is paramount.
Security practitioners should implement immediate mitigations by upgrading to patched PHP versions that address this specific return value handling issue. The fix requires proper validation of OpenSSL function return codes and appropriate error handling mechanisms that prevent negative values from causing interpreter crashes. Organizations should also consider implementing monitoring solutions to detect potential exploitation attempts and ensure that all PHP applications utilizing OpenSSL functionality are updated to secure versions. This vulnerability aligns with CWE-248, which addresses the issue of an exception being thrown but not caught, and relates to ATT&CK technique T1499.004 for network denial of service attacks. The remediation process should include comprehensive testing of applications to ensure that the patched versions maintain expected functionality while eliminating the crash conditions that could be exploited by attackers.