{"id":"CVE-2026-61674","published":"2026-09-21T17:17:36.663","lastModified":"2026-09-21T19:17:07.067","description":"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.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-121","CWE-787","CWE-843"],"vendors":[],"products":[],"references":[{"url":"https://github.com/fluent/fluent-bit/commit/45486556be9d023e194665e243f156b228e195e0","tags":[]},{"url":"https://github.com/fluent/fluent-bit/pull/11945","tags":[]},{"url":"https://github.com/fluent/fluent-bit/releases/tag/v5.0.8","tags":[]},{"url":"https://github.com/fluent/fluent-bit/security/advisories/GHSA-jrp8-r9hx-gf73","tags":[]},{"url":"https://github.com/fluent/fluent-bit/security/advisories/GHSA-jrp8-r9hx-gf73","tags":[]}],"exploitRefs":[{"url":"https://github.com/fluent/fluent-bit/commit/45486556be9d023e194665e243f156b228e195e0","tags":[]},{"url":"https://github.com/fluent/fluent-bit/pull/11945","tags":[]},{"url":"https://github.com/fluent/fluent-bit/releases/tag/v5.0.8","tags":[]},{"url":"https://github.com/fluent/fluent-bit/security/advisories/GHSA-jrp8-r9hx-gf73","tags":[]},{"url":"https://github.com/fluent/fluent-bit/security/advisories/GHSA-jrp8-r9hx-gf73","tags":[]}],"hasPoc":true,"ai":null}