flex.skl in Will Estes and John Millaway Fast Lexical Analyzer Generator (flex) before 2.5.33 does not allocate enough memory for grammars containing (1) REJECT statements or (2) trailing context rules, which causes flex to generate code that contains a buffer overflow that might allow context-dependent attackers to execute arbitrary code
Published Mar 29, 2006
7.5
HIGHCVSS 2.0
EPSS 4.77%
Description
flex.skl in Will Estes and John Millaway Fast Lexical Analyzer Generator (flex) before 2.5.33 does not allocate enough memory for grammars containing (1) REJECT statements or (2) trailing context rules, which causes flex to generate code that contains a buffer overflow that might allow context-dependent attackers to execute arbitrary code.
Affected products
Remediation
Red Hat statement
This issue only affects parsers which are generated by grammars which either use REJECT or rules with a variable trailing context (in these rules the parser has to keep all backtracking paths). The Red Hat Security Response Team analysed all packages that include flex generated parsers in Red Hat Enterprise Linux (2.1, 3, and 4) and found none were vulnerable.
Metrics
No CVSS v4.0 score for this CVE.
No CVSS v3.1 score for this CVE.
No CVSS v3.0 score for this CVE.
AV:N/AC:L/Au:N/C:P/I:P/A:P
This CVE is not in the KEV list.
No CISA SSVC assessment for this CVE yet.
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2022–2026- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Percentile over time
- EPSS v2
- EPSS v3
- EPSS v4
- EPSS v5
Table of values (11 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 4.77% (0.04769) | 91.63th | v5 (v2026.06.15) |
| Jun 15, 2026 | 4.77% (0.04769) | 90.73th | v5 (v2026.06.15) |
| Mar 30, 2025 | 4.56% (0.04557) | 88.16th | v4 (v2025.03.14) |
| Mar 29, 2025 | 7.11% (0.07113) | 85.56th | v4 (v2025.03.14) |
| Mar 17, 2025 | 5.38% (0.05378) | 89.39th | v4 (v2025.03.14) |
| Dec 12, 2024 | 3.84% (0.03841) | 92.25th | v3 (v2023.03.01) |
| Oct 7, 2023 | 3.84% (0.03841) | 90.81th | v3 (v2023.03.01) |
| Mar 7, 2023 | 2.80% (0.02798) | 89.01th | v3 (v2023.03.01) |
| Mar 6, 2023 | 4.42% (0.04421) | 88.21th | v2 (v2022.01.01) |
| Apr 1, 2022 | 4.42% (0.04421) | 87.03th | v2 (v2022.01.01) |
| Feb 4, 2022 | 4.42% (0.04421) | 70.83th | v2 (v2022.01.01) |
References (17)
- http://prdownloads.sourceforge.net/flex/flex-2.5.33.tar.bz2?download x_refsource_CONFIRMProduct
- http://secunia.com/advisories/19071 third-party-advisoryx_refsource_SECUNIAPatchVendor Advisory
- http://secunia.com/advisories/19126 third-party-advisoryx_refsource_SECUNIAVendor Advisory
- http://secunia.com/advisories/19228 third-party-advisoryx_refsource_SECUNIAVendor Advisory
- http://secunia.com/advisories/19424 third-party-advisoryx_refsource_SECUNIAPatchVendor Advisory
- http://securityreason.com/securityalert/570 third-party-advisoryx_refsource_SREASONThird Party Advisory
- http://sourceforge.net/mailarchive/forum.php?thread_name=20060223020346.GA11231%40tabitha.home.tldz.org&forum_name=flex-announce mailing-listx_refsource_MLISTRelease Notes
- http://www.gentoo.org/security/en/glsa/glsa-200603-07.xml vendor-advisoryx_refsource_GENTOOThird Party Advisory
- http://www.osvdb.org/23440 vdb-entryx_refsource_OSVDBBroken LinkPatch
- http://www.securityfocus.com/bid/16896 vdb-entryx_refsource_BIDPatchThird Party AdvisoryVDB Entry
- http://www.us.debian.org/security/2006/dsa-1020 vendor-advisoryx_refsource_DEBIANPatchVendor Advisory
- http://www.vupen.com/english/advisories/2006/0770 vdb-entryx_refsource_VUPENBroken LinkURL Repurposed
- https://access.redhat.com/security/cve/CVE-2006-0459 Vendor Advisory
- https://exchange.xforce.ibmcloud.com/vulnerabilities/24995 vdb-entryx_refsource_XFVDB Entry
- https://nvd.nist.gov/vuln/detail/CVE-2006-0459
- https://usn.ubuntu.com/260-1/ vendor-advisoryx_refsource_UBUNTUThird Party Advisory
- https://www.cve.org/CVERecord?id=CVE-2006-0459
Change history (0)
No recorded changes yet.