--- cve: "CVE-2026-61674" severity: "CRITICAL" cvss: 9.2 epss: "62.7%" vendor: "fluent" kev: false exploited: false published: "2026-09-21 17:17:36" tags: [cve, security, critical] source: tsecurity.de CVE-Dossier exported: "2026-09-22T03:49:35+02:00" --- # CVE-2026-61674 > 9.2 CRITICAL · 🧪 PoC ## Beschreibung Fluent Bit is a fast and lightweight logs, metrics, and traces processor for Linux, BSD, macOS, and Windows. From 0.11.0 until 5.0.8, plugins/out_forward/forward.c secure_forward_pong copies the server-controlled PONG[2] reason into the 32-byte stack buffer msg with memcpy without checking its MessagePack type or length. An attacker who controls or can impersonate an out_forward Secure Forward destination configured with Shared_Key or Empty_Shared_Key can send an oversized reason during the first handshake and overwrite stack control data. Protected builds reliably terminate, while builds without a stack canary or with a disclosure can allow remote code execution as the Fluent Bit process user. When the opt-in --supervisor mode is used, fork-only respawns preserve the canary and address layout, allowing repeated crash-or-survive probes to support code execution on a hardened build; ordinary exec-based or service-manager restarts do not preserve that state. This issue is fixed in version 5.0.8. ## CVSS-Vektor ``` CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N ``` | Metrik | Wert | Bewertung | |---|---|---| | AV Angriffsvektor | Netzwerk | bad | | AC Komplexität | Gering | bad | | PR Privilegien | Keine | bad | | UI Interaktion | Keine | bad | ## Referenzen - - - - --- _Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-61674) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_