CVE-2026-63387 — CVE & Security Advisory Radar

🎯 CVE-2026-63387 🧪 PoC 🇪🇺 EUVD

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CVE-2026-63387 | 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 P

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.

Klassifikation & Betroffenheit:

libevent libevent < 2.1.13libevent 2.2.0-alpha, < 2.2.2-alpha

Improper Restriction of Operations within the Bounds of a Memory Buffer 🎯 High

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

🛡️ Empfohlene Mitigation: Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow prot…

Vollständige Definition bei MITRE ➔

⚔️ Typische Angriffsmuster (CAPEC):

CAPEC-10 · Buffer Overflow via Environment Variable… (High) CAPEC-14 · Client-side Injection-induced Buffer Ove… (High) CAPEC-24 · Filter Failure through Buffer Overflow (High) CAPEC-42 · MIME Conversion (High) CAPEC-44 · Overflow Binary Resource File (Very High) CAPEC-45 · Buffer Overflow via Symbolic Links (High) CAPEC-100 · Overflow Buffers (Very High) CAPEC-123 · Buffer Manipulation (Very High)

🧩 Ähnliche Schwachstellen (Hersteller/Klasse/Score-Band):

CVE-2026-63388 8.4 CVE-2026-63495 7.5 CVE-2026-63379 6.3 CVE-2026-63381 5.8 CVE-2026-63380 5.7

🩹 Patch verfügbar (OSV):

🩹 df3ecad3a040fd6d4fad4287defe113395de6fd7 (Commit) 🩹 79ddfb460847999b807cba76d04e73891f29c6ee (Commit)

📰 Eigene Berichterstattung: ➔ CVE-2026-63387 | Libevent up to 2.1.12/2.2.1 DNS Server Request Formatting evdns

📚 Referenzen & Quellen:

🇪🇺 Original-Eintrag (ENISA EUVD) 🇺🇸 NVD-Eintrag

Ausnutzungs-Zeitleiste:

Reserviert 2026

Veröffentlicht 08/2026

Heute 26.09.

CVSS-Vektor-Analyse: 7.0

AV · Angriffsvektor Netzwerk

AC · Komplexität Hoch

PR · Privilegien Keine

UI · Interaktion Keine

S · Scope Unverändert

C · Vertraulichkeit Gering

I · Integrität Gering

A · Verfügbarkeit Hoch

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

Veröffentlicht:20.08.2026

Aktualisiert:09.09.2026 21:19

Assigner (CNA):GitHub_M

EUVD-ID:EUVD-2026-63508

Quellen: 🇪🇺 EUVD-Datenbank (ENISA) + 🇺🇸 NVD-Anreicherung · 24-h-Cache

CWE-119: Memory Corruption ✓ Offizieller Patch / Advisory verfügbar

💡 Gegenmaßnahme: Sicherheits-Update des Herstellers zeitnah einspielen und Netzwerksegmentierung prüfen.

Tier	2026-09-12	2026-09-25
≥90 %	0	497
≥50 %	0	1468
≥10 %	0	0
<10 %	300	1

EPSS

0.4%

CVE-2026-63387 🌐 Netzwerk (Remote) 🔓 Keine Authentifizierung nötig

libevent

CVE-2026-63387 | 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 P

CWE-119: Memory Corruption ✓ Offizieller Patch / Advisory verfügbar

💡 Gegenmaßnahme: Sicherheits-Update des Herstellers zeitnah einspielen und Netzwerksegmentierung prüfen.

20.08.2026

🛡️ Details ➔

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