zlib 1.3.1.2 through 1.3.2 Heap Buffer Overflow via gz_vacate
CVE-2026-85091 is fixed in 7 products on 1 platform, first by lib32z1 1:1.3.dfsg-3.1ubuntu2.3, released September 3, 2026. It is not reported as exploited. Patch Radar priority: High.
zlib versions 1.3.1.2 through 1.3.2 contain a heap buffer overflow vulnerability in the gz_vacate() function when processing non-blocking gzwrite() operations with stale external buffer pointers. Attackers can trigger the overflow by calling gzprintf() or gzvprintf() after a write stall, causing an unchecked memmove() to write beyond the internal input buffer boundary.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| lib32z1 · Ubuntu 24.04.5 LTS (noble) | 1:1.3.dfsg-3.1ubuntu2.3 | lib32z1 1:1.3.dfsg-3.1ubuntu2.3 | Sep 3, 2026 |
| lib32z1 · Ubuntu 26.04.1 LTS (resolute) | 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | lib32z1 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | Sep 3, 2026 |
| lib64z1 · Ubuntu 24.04.5 LTS (noble) | 1:1.3.dfsg-3.1ubuntu2.3 | lib64z1 1:1.3.dfsg-3.1ubuntu2.3 | Sep 3, 2026 |
| lib64z1 · Ubuntu 26.04.1 LTS (resolute) | 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | lib64z1 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | Sep 3, 2026 |
| libminizip1t64 · Ubuntu 24.04.5 LTS (noble) | 1:1.3.dfsg-3.1ubuntu2.3 | libminizip1t64 1:1.3.dfsg-3.1ubuntu2.3 | Sep 3, 2026 |
| libminizip1t64 · Ubuntu 26.04.1 LTS (resolute) | 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | libminizip1t64 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | Sep 3, 2026 |
| libx32z1 · Ubuntu 24.04.5 LTS (noble) | 1:1.3.dfsg-3.1ubuntu2.3 | libx32z1 1:1.3.dfsg-3.1ubuntu2.3 | Sep 3, 2026 |
| libx32z1 · Ubuntu 26.04.1 LTS (resolute) | 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | libx32z1 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | Sep 3, 2026 |
| minizip · Ubuntu 24.04.5 LTS (noble) | 1:1.3.dfsg-3.1ubuntu2.3 | minizip 1:1.3.dfsg-3.1ubuntu2.3 | Sep 3, 2026 |
| minizip · Ubuntu 26.04.1 LTS (resolute) | 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | minizip 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | Sep 3, 2026 |
| zlib · Debian 13.5 (trixie) | 1:1.3.dfsg+really1.3.1-1+deb13u1 | DEBIAN-CVE-2026-85091 | Sep 3, 2026 |
| zlib · Debian 14 | 1:1.3.dfsg+really1.3.2-4 | DEBIAN-CVE-2026-85091 | Sep 3, 2026 |
| zlib1g · Ubuntu 24.04.5 LTS (noble) | 1:1.3.dfsg-3.1ubuntu2.3 | zlib1g 1:1.3.dfsg-3.1ubuntu2.3 | Sep 3, 2026 |
| zlib1g · Ubuntu 26.04.1 LTS (resolute) | 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | zlib1g 1:1.3.dfsg+really1.3.1-1ubuntu3.2 | Sep 3, 2026 |
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