https://github.com/madler/zlib/releases/tag/v1.4 lists these security fixes:
* Non-blocking gzwrite() had a buffer overflow; CVE-2026-85091 (reported by mat-mo; also TOB-ZLIB-003). * inflateGetDictionary() could write up to 8 MB past the caller's 32K buffer (Theorem THM-ZLIB-001). This took a zlib header with an invalid window size, then inflateReset() or inflateSync(). Affects 1.3.1 and 1.3.2. * inflateSync() before the window size was known allocated a one-byte window that could later be overrun (TOB-ZLIB-004). * inflatePrime() could lead inflate() to read before the start of the input (TOB-ZLIB-014). * Repeated deflatePrime() calls could write past the pending buffer (TOB-ZLIB-013). * inflateBack() failed to detect distances too far back, and copied uninitialized memory to the output (reported by Kornel Lesiński). * gzseek() forward before any data was written could write uninitialized memory to the gzip output (found by Claude Opus 5.5). * deflateResetKeep() used mid-stream could read outside the window (reported by Jason Gross). * gzdopen() now sets close-on-exec with the correct flag (TOB-ZLIB-008).* minizip: * A double free in block_central_name() (reported by Oculytic), and a NULL dereference on repeated zipAlreadyThere() calls after a bad central directory (reported by Naveed Khan). * Validation of extra-field sizes, plus portable, alignment-safe reading, in zipRemoveExtraInfoBlock() (reported by Naveed Khan and jmestwa-coder). * unzip no longer reads Zip64 values from outside their extra-field record (reported by Mohamed Elnady). It also uses only the Zip64 locator immediately before the end of central directory record (reported by snajafov). Crafted archives could make minizip report different entries than other readers. * miniunz could create directories outside the extraction directory (reported by Naveed Khan), and on Windows write files anywhere (reported by Trail of Bits). Fixed by Naveed Khan. Path names are now processed by component. * contrib/infback9: removed out-of-bounds pointer arithmetic in inftree9.c; CVE-2026-4738 (fix by npt-1707, submitted by CrossVR). The pointers return in bounds before use and no known compiler mishandles this, so the critical rating overstates it, though it could trap on capability hardware such as CHERI.
