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Vulnerability record · CVE-2019-6293 · published 15 January 2019

CVE-2019-6293: Westes flex vulnerability

Westes · Flex

An issue was discovered in the function mark_beginning_as_normal in nfa.c in flex 2.6.4. There is a stack exhaustion problem caused by the mark_beginning_as_normal function making recursive calls to itself in certain scenarios involving lots of '*' characters. Remote attackers could leverage this vulnerability to cause a denial-of-service.

5.5 CVSS 3.0 Medium EPSS 1.6% · top 25.1% CWE-674 · CWE-674
5.5CVSS 3.0 base score, v2 4.3
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

An issue was discovered in the function mark_beginning_as_normal in nfa.c in flex 2.6.4. There is a stack exhaustion problem caused by the mark_beginning_as_normal function making recursive calls to itself in certain scenarios involving lots of '*' characters. Remote attackers could leverage this vulnerability to cause a denial-of-service.

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/westes/flex/issues/414 ExploitThird Party Advisory
https://github.com/westes/flex/issues/414 ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2016-6354Debian linux memory buffer overflow vulnerabilityHeap-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 servi…EPSS 8.8%7.5CVE-2006-0459Westes flex memory buffer overflow vulnerabilityflex.skl in Will Estes and John Millaway Fast Lexical Analyzer Generator (flex) before 2.5.33 does not allocate enough memory for grammars containing…EPSS 4.8%

Source: NIST National Vulnerability Database (record CVE-2019-6293), CISA KEV, FIRST EPSS (scores of 2026-10-02). This page is refreshed as NVD updates the record.