CVE-2016-6354

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-17. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 9%CVSS: 9.8Exploit: None knownExposed: 0

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

Heap-based buffer overflow in the yy_get_next_buffer function in Flex before 2.6.1 might allow context-dependent attackers to cause a denial of service or possibly execute arbitrary code via vectors involving num_to_read.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
52(Track)
EG Risk 52/100SSVC: 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
Severity98% × 45%
Exploitation9% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
9%
EPSS %ILE
95%
KEV
Not listed

Published

September 21, 2016

Last Modified

June 17, 2026

Advisory Details (5)

Auto-updated Sep 23, 2026
Patch available. Sources: github_commit.
generic

flex: Potential insecure code generation (GLSA 201701-31) — Gentoo security

https://security.gentoo.org/glsa/201701-31
github_commit Patch Available

commit a5cbe929ac32 (westes/flex)

Patch available: westes/flex v2.6.1 (contains commit a5cbe929ac32)

https://github.com/westes/flex/commit/a5cbe929ac3255d371e698f62dc256afe7006466
generic

oss-security - Re: CVE request: flex: Buffer overflow in generated code (yy_get_next_buffer)

http://www.openwall.com/lists/oss-security/2016/07/26/12
generic

oss-security - CVE request: flex: Buffer overflow in generated code (yy_get_next_buffer)

http://www.openwall.com/lists/oss-security/2016/07/18/8
generic

[SECURITY] [DSA 3653-1] flex security update

http://www.debian.org/security/2016/dsa-3653

Affected Packages

(8 across 8 ecosystems)
Alpine:v3.2(1)
PackageVulnerable rangeFixed inDependents
flex2.5.35-r1 ... 2.5.39-r0 (8 versions)2.5.39-r1—
Alpine:v3.3(1)
PackageVulnerable rangeFixed inDependents
flex2.5.35-r1 ... 2.5.39-r2 (10 versions)2.5.39-r3—
Alpine:v3.4(1)
PackageVulnerable rangeFixed inDependents
flex2.5.35-r1 ... 2.6.0-r0 (11 versions)2.6.1-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
flex—2.6.1-1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
flex—2.6.1-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
flex—2.6.1-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
flex—2.6.1-1—
Debian:8(1)
PackageVulnerable rangeFixed inDependents
flex2.5.39-8, 2.5.39-8+deb8u12.5.39-8+deb8u2—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 22× 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.

Showing the most recent 100 of 149 total refreshes for this CVE.

  1. 2026-09-24 13:59 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2016-6354?
CVE-2016-6354 is a critical vulnerability published on September 21, 2016. Heap-based buffer overflow in the yygetnextbuffer function in Flex before 2.6.1 might allow context-dependent attackers to cause a denial of service or possibly execute arbitrary code via vectors involving numto_read.
When was CVE-2016-6354 disclosed?
CVE-2016-6354 was first published in the National Vulnerability Database on September 21, 2016, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2016-6354 actively exploited?
CVE-2016-6354 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 9% probability of exploitation in the next 30 days, which ranks it in the top 5.0% of all scored CVEs.
What is the CVSS score of CVE-2016-6354?
CVE-2016-6354 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2016-6354?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2016-6354, 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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