CVE-2021-23017 — CVE & Security Advisory Radar

🎯 CVE-2021-23017 LOW 3.1 🔥 EPSS 53.5% 🧪 PoC 🇪🇺 EUVD

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CVE-2021-23017 | A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

Klassifikation & Betroffenheit:

n/a Nginx Web Server, Nginx Plus Nginx Web Server versions 0.6.18 thru 1.20.0 before 1.20.1, Nginx plus versions R13 thru R23 before R23 P1. Nginx plus version R24 before R24 P1f5 nginx *openresty openresty *fedoraproject fedora 33fedoraproject fedora 34oracle blockchain_platform *oracle communications_control_plane_monitor 3.4oracle communications_control_plane_monitor 4.2

Improper Control of Generation of Code ('Code Injection') 🎯 Medium

The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

🛡️ Empfohlene Mitigation: Refactor your program so that you do not have to dynamically generate code.

Vollständige Definition bei MITRE ➔

⚔️ Typische Angriffsmuster (CAPEC):

CAPEC-35 · Leverage Executable Code in Non-Executab… (Very High) CAPEC-77 · Manipulating User-Controlled Variables (Very High) CAPEC-242 · Code Injection (High)

🎯 ATT&CK-Techniken (Kill-Chain-Verhalten):

T1027.006 · Obfuscated Files or Information: H… T1027.009 · Obfuscated Files or Information: E… T1564.009 · Hide Artifacts: Resource Forking

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

CVE-2025-59320 4.6 CVE-2026-35502 4.6 CVE-2026-20765 4.6 CVE-2026-20763 4.6 CVE-2026-67673 4.6

🧪 Exploit-Evidenz: EDB-50973 · Nginx 1.20.0 - Denial of Service (DOS)

🐙 niandy/nginx-patch 🐙 M507/CVE-2021-23017-PoC 🐙 lakshit1212/CVE-2021-23017-PoC 🐙 ShivamDey/CVE-2021-23017 🐙 z3usx01/CVE-2021-23017-POC

🩹 Patch verfügbar (OSV):

🩹 98a892514206ee63d418d9f355c92b6d4ce6113a (Commit) 🩹 a1017ea9856315486e24f8712d7b20dfd5312ceb (Commit)

📚 Referenzen & Quellen:

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

Ausnutzungs-Zeitleiste:

Reserviert 2021

Veröffentlicht 06/2021

Heute 16.09.

Veröffentlicht:01.06.2021

Aktualisiert:17.06.2026 03:38

Assigner (CNA):f5

EUVD-ID:EUVD-2021-10135

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

CWE-94: Code Injection ✓ Offizieller Patch / Advisory verfügbar

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

Tier	2026-08-29	2026-09-16
≥90 %	4	0
≥50 %	4	0
≥10 %	3	0
<10 %	304	300

Datenquellen & Methodik: Primärquelle ist die EUVD der ENISA (laufender Datenbank-Sync, alle 15 Minuten), abgeglichen mit dem CISA-KEV-Katalog und der NVD — Detail-Dossiers reichern fehlende Felder live per NVD an — mit Fallback auf CIRCL vulnerability-lookup (EU/Non-Profit, aggregiert CVE-, GitHub- und OSV-Advisories). Der CISA-KEV-Katalog (Known Exploited Vulnerabilities, ~1.700 aktiv ausgenutzte Schwachstellen) wird bei jedem Sync vollständig neu geladen und kreuzreferenziert — filterbar über die KEV-Pille. CVSS 3.1 wird nach Ampel-Logik aus Verteidigersicht dekodiert; EPSS bezeichnet die 30-Tage-Exploit-Wahrscheinlichkeit (FIRST.org).

🇪🇺 ENISA EUVD 🇺🇸 NVD ⚠️ CISA KEV ⚡ EPSS

3.1 LOW

🇪🇺 EUVD

EPSS

53.5%

CVE-2021-23017 🌐 Netzwerk (Remote) 🔓 Keine Authentifizierung nötig

🧪 n/a

CVE-2021-23017 | A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

CWE-94: Code Injection ✓ Offizieller Patch / Advisory verfügbar

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

01.06.2021

🛡️ Details ➔

CVE-2021-23017 | A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

Zero-Day & Vulnerability Intelligence Hub

CVE-2021-23017 | A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.