---
cve: "CVE-2026-63387"
severity: "HIGH"
cvss: 7.0
epss: "0.4%"
vendor: "libevent"
kev: false
exploited: false
published: "2026-08-20 18:16:36"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-26T20:19:33+02:00"
---

# CVE-2026-63387

> 7.0 HIGH · 🧪 PoC

## Beschreibung

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an off-by-one stack buffer overflow in evdns.c when dnsname_to_labels formats a name-bearing DNS record at the end of the 64 KB stack buffer allocated by evdns_server_request_format_response. The final-label check permits j plus label_len plus one to equal buf_len, after which the terminating null byte is written to buf[buf_len]. A crafted DNS server response containing PTR, CNAME, MX, NS, or SOA data can trigger the one-byte out-of-bounds write and crash or corrupt the process. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Gering | warn |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- df3ecad3a040fd6d4fad4287defe113395de6fd7 (Commit)
- 79ddfb460847999b807cba76d04e73891f29c6ee (Commit)

## Referenzen

- <https://github.com/libevent/libevent/security/advisories/GHSA-58rx-7448-jw47>
- <https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable>
- <https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-63387) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_