{"id":"UBUNTU-CVE-2026-85091","details":"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.","modified":"2026-09-16T11:43:10Z","published":"2026-09-03T13:06:00Z","upstream":["CVE-2026-85091"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-85091"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-85091"},{"type":"REPORT","url":"https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490"},{"type":"REPORT","url":"https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate"}],"affected":[{"package":{"name":"klibc","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/klibc?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.1-3.1ubuntu2","2.0.2-1ubuntu1","2.0.2-1ubuntu2","2.0.3-0ubuntu1","2.0.3-0ubuntu1.14.04.1","2.0.3-0ubuntu1.14.04.2","2.0.3-0ubuntu1.14.04.3","2.0.3-0ubuntu1.14.04.3+esm2","2.0.3-0ubuntu1.14.04.3+esm3","2.0.3-0ubuntu1.14.04.3+esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"klibc-utils","binary_version":"2.0.3-0ubuntu1.14.04.3+esm4"},{"binary_name":"libklibc","binary_version":"2.0.3-0ubuntu1.14.04.3+esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85091.json"}},{"package":{"name":"zlib","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/zlib?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:1.2.8.dfsg-1ubuntu1","1:1.2.8.dfsg-1ubuntu1.1","1:1.2.8.dfsg-1ubuntu1.1+esm1","1:1.2.8.dfsg-1ubuntu1.1+esm2","1:1.2.8.dfsg-1ubuntu1.1+esm3"],"ecosystem_specific":{"binaries":[{"binary_version":"1:1.2.8.dfsg-1ubuntu1.1+esm3","binary_name":"lib32z1"},{"binary_name":"lib64z1","binary_version":"1:1.2.8.dfsg-1ubuntu1.1+esm3"},{"binary_name":"libx32z1","binary_version":"1:1.2.8.dfsg-1ubuntu1.1+esm3"},{"binary_version":"1:1.2.8.dfsg-1ubuntu1.1+esm3","binary_name":"zlib-bin"},{"binary_name":"zlib1g","binary_version":"1:1.2.8.dfsg-1ubuntu1.1+esm3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85091.json"}},{"package":{"name":"klibc","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/klibc?arch=source&distro=esm-infra%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.3-0ubuntu1","2.0.4-4","2.0.4-6","2.0.4-7","2.0.4-8","2.0.4-8ubuntu1","2.0.4-8ubuntu1.16.04.1","2.0.4-8ubuntu1.16.04.2","2.0.4-8ubuntu1.16.04.3","2.0.4-8ubuntu1.16.04.4","2.0.4-8ubuntu1.16.04.4+esm1","2.0.4-8ubuntu1.16.04.4+esm2","2.0.4-8ubuntu1.16.04.4+esm3"],"ecosystem_specific":{"binaries":[{"binary_name":"klibc-utils","binary_version":"2.0.4-8ubuntu1.16.04.4+esm3"},{"binary_name":"libklibc","binary_version":"2.0.4-8ubuntu1.16.04.4+esm3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85091.json"}},{"package":{"name":"rsync","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/rsync?arch=source&distro=esm-infra-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.1-3","3.1.1-3ubuntu1","3.1.1-3ubuntu1.1","3.1.1-3ubuntu1.2","3.1.1-3ubuntu1.3","3.1.1-3ubuntu1.3+esm1","3.1.1-3ubuntu1.3+esm2","3.1.1-3ubuntu1.3+esm3","3.1.1-3ubuntu1.3+esm4","3.1.1-3ubuntu1.3+esm5","3.1.1-3ubuntu1.3+esm6"],"ecosystem_specific":{"binaries":[{"binary_name":"rsync","binary_version":"3.1.1-3ubuntu1.3+esm6"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85091.json"}},{"package":{"name":"zlib","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/zlib?arch=source&distro=esm-infra%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:1.2.8.dfsg-2ubuntu4","1:1.2.8.dfsg-2ubuntu4.1","1:1.2.8.dfsg-2ubuntu4.3","1:1.2.8.dfsg-2ubuntu4.3+esm1","1:1.2.8.dfsg-2ubuntu4.3+esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"1:1.2.8.dfsg-2ubuntu4.3+esm2","binary_name":"lib32z1"},{"binary_name":"lib64z1","binary_version":"1:1.2.8.dfsg-2ubuntu4.3+esm2"},{"binary_version":"1:1.2.8.dfsg-2ubuntu4.3+esm2","binary_name":"libx32z1"},{"binary_version":"1:1.2.8.dfsg-2ubuntu4.3+esm2","binary_name":"zlib1g"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85091.json"}},{"package":{"name":"zsync","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/zsync?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.2-1ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"zsync","binary_version":"0.6.2-1ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-85091.json"}},{"package":{"name":"klibc","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/klibc?arch=source&di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