CVE-2026-61674

CRITICALPre-NVD 9.29.2—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.9%, top 44% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this weekElevated
9.2EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.2Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
9.2
EG Score
9.2(medium)
EG Risk
57(Track*)
EG Risk 57/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity92% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
1%
EPSS %ILE
56%
KEV
Not listed

Published

September 21, 2026

Last Modified

September 24, 2026

Advisory Details (4)

Auto-updated Sep 21, 2026
🔬 Proof of concept available. Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available

Fluent Bit 5.0.8

Patch available: fluent/fluent-bit v5.0.8

https://github.com/fluent/fluent-bit/releases/tag/v5.0.8
github_commit Patch Available

commit 45486556be9d (fluent/fluent-bit)

Patch available: fluent/fluent-bit v5.0.8 (contains commit 45486556be9d)

https://github.com/fluent/fluent-bit/commit/45486556be9d023e194665e243f156b228e195e0
github_pr Patch Available

out_forward: process type and length of pong strictly

Patch available: fluent/fluent-bit v5.0.8 (PR #11945 merged 2026-06-15)

https://github.com/fluent/fluent-bit/pull/11945
github Patch Available🟡 PoC Available

Remote stack buffer overflow in Fluent Bit `out_forward` Secure-Forward `PONG` handler · Advisory · fluent/fluent-bit · GitHub

https://github.com/fluent/fluent-bit/security/advisories/GHSA-jrp8-r9hx-gf73

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 9× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-24 15:04 UTCEG score recompute
  2. 2026-09-23 19:08 UTCEG score recompute
  3. 2026-09-23 17:54 UTCEPSS rescore
  4. 2026-09-22 19:17 UTCEG score recompute
  5. 2026-09-21 19:29 UTCEG score recompute
  6. 2026-09-21 19:00 UTCEG score recompute
  7. 2026-09-21 17:25 UTCEG score recompute
  8. 2026-09-21 16:25 UTCEG score recompute
  9. 2026-09-21 16:25 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-61674?
CVE-2026-61674 is a critical vulnerability published on September 21, 2026. 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/outforward/forward.c secureforwardpong copies the server-controlled PONG[2] reason into the 32-byte stack buffer msg with memcpy without checking its…
When was CVE-2026-61674 disclosed?
CVE-2026-61674 was first published in the National Vulnerability Database on September 21, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-61674 actively exploited?
CVE-2026-61674 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 43.5% of all scored CVEs.
What is the CVSS score of CVE-2026-61674?
CVE-2026-61674 has a CVSS v3 base score of 9.2 (NVD).
How do I remediate CVE-2026-61674?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-61674, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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