CVE-2026-85091

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.

Database specific

{
    "cna_assigner":  "VulnCheck",
    "cwe_ids":  [
        "CWE-787"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85091.json"
}

References

Affected packages

Git / github.com/madler/zlib

Affected ranges

Type

GIT

Repo

https://github.com/madler/zlib

Events

Introduced

570720b0c24f9686c33f35a1b3165c1f568b96be

Fixed

da607da739fa6047df13e66a2af6b8bec7c2a498

Database specific

Show details

{
    "extracted_events":  [
        {
            "introduced":  "1.3.1.2"
        },
        {
            "last_affected":  "1.3.2"
        },
        {
            "fixed":  "1.3.2"
        }
    ],
    "source":  [
        "AFFECTED_FIELD",
        "DESCRIPTION"
    ]
}

Affected versions

v1.*

v1.3.1.2

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-85091.json"