CVE-2026-85091
zlib Heap Buffer Overflow
Description
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.
INFO
Published Date :
Sept. 3, 2026, 2:20 a.m.
Last Modified :
Sept. 3, 2026, 2:20 a.m.
Remotely Exploit :
Yes !
Source :
None
Affected Products
The following products are affected by CVE-2026-85091
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update zlib to a version that includes the fix.
- Avoid non-blocking gzwrite() with stale pointers.
- Apply vendor-supplied patches when available.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-85091.
| URL | Resource |
|---|---|
| https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490 | technical-description exploit |
| https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393 | technical-description |
| https://github.com/madler/zlib | product |
| https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate | third-party-advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-85091 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-85091
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-85091 vulnerability anywhere in the article.