---
cve: "CVE-2026-76844"
severity: "HIGH"
cvss: 8.3
epss: "0.5%"
vendor: "zlib"
kev: false
exploited: false
published: "2026-08-24 14:17:02"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-10-04T11:19:22+02:00"
---

# CVE-2026-76844

> 8.3 HIGH · 🧪 PoC

## Beschreibung

zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller's buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call.

## CNA-Record (Kanon, cvelistV5)

- CNA: **VulnCheck**
- State: PUBLISHED
- Stand: 2026-10-01 11:03:59
- CNA-CVSS: **8.3** (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **poc**
  - Automatable: **no**
  - Technical Impact: **partial**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- da607da739fa6047df13e66a2af6b8bec7c2a498 (Commit)
- 570720b0c24f9686c33f35a1b3165c1f568b96be (Commit)

## Referenzen

- <https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490>
- <https://github.com/madler/zlib/commit/df84af25dc1942490e1d1c899a07619152a46148>
- <https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393>
- <https://github.com/madler/zlib>
- <https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-76844) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_