CVE-2017-11146 in PHP
Summary
by MITRE
In PHP through 5.6.31, 7.x through 7.0.21, and 7.1.x through 7.1.7, lack of bounds checks in the date extension's timelib_meridian parsing code could be used by attackers able to supply date strings to leak information from the interpreter, related to ext/date/lib/parse_date.c out-of-bounds reads affecting the php_parse_date function. NOTE: this vulnerability exists because of an incomplete fix for CVE-2017-11145.
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Analysis
by VulDB Data Team • 12/12/2022
The vulnerability identified as CVE-2017-11146 represents a critical out-of-bounds read flaw within PHP's date extension that affects multiple versions including 5.6.31 and earlier, 7.0.21 and earlier, and 7.1.7 and earlier. This vulnerability specifically targets the timelib_meridian parsing functionality within the ext/date/lib/parse_date.c file, where the php_parse_date function fails to properly validate input boundaries when processing date strings. The flaw stems from an incomplete remediation of a similar vulnerability documented in CVE-2017-11145, creating a persistent security weakness that attackers can exploit through carefully crafted date inputs.
The technical implementation of this vulnerability occurs within the date parsing subsystem where the timelib_meridian function processes time zone and meridian indicators such as am/pm values. When PHP encounters malformed or specially crafted date strings, the parsing code does not perform adequate bounds checking on memory accesses, leading to potential information disclosure through out-of-bounds memory reads. This memory access pattern can reveal sensitive data from the interpreter's memory space including stack contents, heap data, or other internal state information that may contain cryptographic keys, session data, or other confidential information.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential pathways for more sophisticated exploitation techniques. The leaked memory information could be used to bypass security mechanisms, understand memory layout patterns, or facilitate further attacks such as heap spraying or return-oriented programming attacks. The vulnerability affects PHP applications that process user-supplied date inputs, making it particularly dangerous in web applications where date parsing is commonly used for timestamp validation, calendar functionality, or user registration systems. Attackers can leverage this flaw by submitting malformed date strings that trigger the vulnerable parsing code path, potentially exposing sensitive application internals.
Security mitigations for this vulnerability require immediate patching of affected PHP versions to the latest stable releases that contain proper bounds checking implementations. Organizations should implement input validation measures that sanitize date string inputs before processing them through PHP's date functions, though this approach provides only partial protection as the underlying vulnerability remains in the core parsing library. Additionally, monitoring and logging of date parsing operations can help detect potential exploitation attempts, while application-level sandboxing techniques may provide defense-in-depth protection. This vulnerability aligns with CWE-129, which covers improper validation of array indices, and relates to ATT&CK technique T1059.007 for command and scripting interpreter usage. The incomplete fix approach demonstrates how remediation efforts can sometimes create new attack surfaces, emphasizing the importance of thorough vulnerability analysis and comprehensive testing of security patches.