Zlib Zlib vulnerabilities

CVE-2026-76844 High · 7.4 CWE-787 Aug 24, 2026

zlib 1.2.11 through 1.3.2 Heap Buffer Overflow via Stale gzwrite Pointer After Failed Write

zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller's buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call.

CVE-2026-27171 Medium · 5.5 CWE-1284 Feb 18, 2026

zlib before 1.3.2 allows CPU consumption via crc32_combine64 and crc32_combine_gen64…

zlib before 1.3.2 allows CPU consumption via crc32_combine64 and crc32_combine_gen64 because x2nmodp can do right shifts within a loop that has no termination condition.

CVE-2026-22184 High · 7.8 CWE-787 Jan 7, 2026

zlib <= 1.3.1.2 untgz Global Buffer Overflow in TGZfname()

zlib versions up to and including 1.3.1.2 include a global buffer overflow in the untgz utility located under contrib/untgz. The vulnerability is limited to the standalone demonstration utility and does not affect the core zlib compression library. The flaw occurs when a user executes the untgz command with an excessively long archive name supplied via the command line, leading to an out-of-bounds write in a fixed-size global buffer.

CVE-2023-45853 Critical · 9.8 CWE-190 Oct 13, 2023

pyminizip affected by zlib's integer overflow/heap based buffer overflow vulnerability due to vulnerable dependency

MiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64 via a long filename, comment, or extra field. NOTE: MiniZip is not a supported part of the zlib product. NOTE: pyminizip through 0.2.6 is also vulnerable because it bundles an affected zlib version, and exposes the applicable MiniZip code through its compress API.

CVE-2022-37434 Critical · 9.8 CWE-787 Aug 5, 2022

zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c...

zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header extra field. NOTE: only applications that call inflateGetHeader are affected. Some common applications bundle the affected zlib source code but may be unable to call inflateGetHeader (e.g., see the nodejs/node reference).

CVE-2018-25032 High · 7.5 CWE-787 Mar 25, 2022

Nokogiri affected by zlib's Out-of-bounds Write vulnerability

zlib before 1.2.12 allows memory corruption when deflating (i.e., when compressing) if the input has many distant matches.

CVE-2016-9841 Critical · 9.8 May 23, 2017

inffast.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified…

inffast.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper pointer arithmetic.

CVE-2016-9840 High · 8.8 May 23, 2017

inftrees.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified…

inftrees.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper pointer arithmetic.