Fluent Bit is a widely used log/telemetry agent across cloud, containers and enterprise infra; a remote code execution in it risks broad compromise of servers and pipelines.
CVE-2026-61674
RCE in Fluent Bit out_forward handshake buffer overflow
Is CVE-2026-61674 being exploited?
Not confirmed. CVE-2026-61674 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked.
How severe is CVE-2026-61674?
CVE-2026-61674 is rated Critical with a CVSS score of 9.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-61674?
Yes. A fix has been recorded for CVE-2026-61674. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-61674 affect?
CVE-2026-61674 affects Fluent Bit 0.11.0 - 5.0.7, out_forward Secure Forward destinations, Linux/BSD/macOS/Windows deployments. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-61674?
Upgrade to Fluent Bit v5.0.8 immediately; restrict/trust Secure Forward endpoints and network access
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution as the Fluent Bit process user via oversized Secure Forward PONG overflow during handshake; can cause crashes or persistent exploitation in supervisor mode.
Immediate action required
- affected>= 0.11.0 and < 5.0.8
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.