Fix: Potential Vulnerability in Cloned Function #4690
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inftrees.c was subtracting an offset from a pointer to an array, in order to provide a pointer that allowed indexing starting at the offset. This is not compliant with the C standard, for which the behavior of a pointer decremented before its allocated memory is undefined. Per the recommendation of a security audit of the zlib code by Trail of Bits and TrustInSoft, in support of the Mozilla Foundation, this tiny optimization was removed, in order to avoid the possibility of undefined behavior.
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Description
This PR fixes a security vulnerability in inflate_table() that was cloned from zlib but did not receive the security patch. The original issue was reported and fixed under madler/zlib@6a04314.
This PR applies the same patch to eliminate the vulnerability.
References
https://nvd.nist.gov/vuln/detail/CVE-2016-9840
madler/zlib@6a04314