CVE-2026-61674 (GCVE-0-2026-61674)

Vulnerability from cvelistv5 – Published: 2026-09-21 16:10 – Updated: 2026-09-21 18:52
VLAI
Title
Fluent Bit: Remote stack buffer overflow in Fluent Bit `out_forward` Secure-Forward `PONG` handler
Summary
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.
Severity
9.2 (Critical)
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
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-21 18:51 UTC
CWE
  • CWE-121 - Stack-based Buffer Overflow
  • CWE-787 - Out-of-bounds Write
  • CWE-843 - Access of Resource Using Incompatible Type ('Type Confusion')
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7763 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
fluent fluent-bit Affected: >= 0.11.0, < 5.0.8
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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