Description
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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | flex | 2.6.1-1 | — |
| Debian 13 | flex | 2.6.1-1 | — |
| Debian 12 | flex | 2.6.1-1 | — |
| Debian 8 | flex | 2.5.39-8+deb8u1 | DSA-3653-2, DSA-3653-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | flex | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | wireshark | 2.2.6-44.3 | SUSE-SU-2017:1442-1 |
| SLES 12 SP1 | MozillaFirefox | 45.3.0esr-78.1 | SUSE-SU-2016:2131-1 |
| SLES 12 SP1 | at | 3.1.14-7.3 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | bogofilter | 1.2.4-5.3 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | cyrus-imapd | 2.3.18-40.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | flex | 2.5.37-8.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | kdelibs4 | 4.12.0-7.3 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | libQtWebKit4 | 4.8.6+2.3.3-3.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | libbonobo | 2.32.1-16.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | mdbtools | 0.7-5.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | netpbm | 10.66.3-4.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | openslp | 2.0.0-11.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | sgmltool | 1.0.9-1075.1 | SUSE-SU-2016:2397-1 |
| SLES 12 SP1 | wireshark | 2.2.6-44.3 | SUSE-SU-2017:1442-1 |
| SLES 12 | MozillaFirefox | 45.3.0esr-78.1 | SUSE-SU-2016:2131-1 |
| SLES 11 SP4 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
| SLES 11 SP3 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 11 SP2 | MozillaFirefox | 45.3.0esr-48.1 | SUSE-SU-2016:2061-1 |
| SLES 11 SP2 | MozillaFirefox-branding-SLED | 45.0-20.38 | SUSE-SU-2016:2061-1 |
| SLES 11 SP2 | firefox-fontconfig | 2.11.0-4.2 | SUSE-SU-2016:2061-1 |
| SLES 11 SP2 | mozilla-nspr | 4.12-25.2 | SUSE-SU-2016:2061-1 |
| SLES 11 SP2 | mozilla-nss | 3.21.1-26.2 | SUSE-SU-2016:2061-1 |
| SLES for SAP 12 SP2 | wireshark | 2.2.6-44.3 | SUSE-SU-2017:1442-1 |
| SLES for SAP 12 SP1 | MozillaFirefox | 45.3.0esr-78.1 | SUSE-SU-2016:2131-1 |
| SLES for SAP 12 SP1 | at | 3.1.14-7.3 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | cyrus-imapd | 2.3.18-40.1 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | flex | 2.5.37-8.1 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | kdelibs4 | 4.12.0-7.3 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | libQtWebKit4 | 4.8.6+2.3.3-3.1 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | libbonobo | 2.32.1-16.1 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | netpbm | 10.66.3-4.1 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | openslp | 2.0.0-11.1 | SUSE-SU-2016:2397-1 |
| SLES for SAP 12 SP1 | wireshark | 2.2.6-44.3 | SUSE-SU-2017:1442-1 |
| SLES for SAP 12 | MozillaFirefox | 45.3.0esr-78.1 | SUSE-SU-2016:2131-1 |
| SLES for SAP 11 SP4 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
| SUSE Package Hub 12 | MozillaThunderbird | 45.3.0-9.1 | openSUSE-SU-2016:2254-1, openSUSE-SU-2016:2253-1 |
| SUSE OpenStack Cloud 5 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
| SUSE Manager Proxy 2.1 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
| SUSE Manager 2.1 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | MozillaFirefox | 45.3.0esr-50.1 | SUSE-SU-2016:2195-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | MozillaFirefox | 50.1.0-1.1 | openSUSE-SU-2024:10071-1 |
| openSUSE Tumbleweed | MozillaThunderbird | 45.5.1-1.1 | openSUSE-SU-2024:10230-1 |
| openSUSE Tumbleweed | firefox-esr | 128.5.1-1.1 | openSUSE-SU-2024:14572-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.4 | flex | 2.6.1-r0 | — |
| Alpine v3.3 | flex | 2.5.39-r3 | — |
| Alpine v3.2 | flex | 2.5.39-r1 | — |
Advisories 12
- DSA-3653-1 flex - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-3653-2 flex - security update Debian Security (DSA / DLA) · Mar 9, 2026
- SUSE-SU-2017:1442-1 Security update for wireshark SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10230-1 MozillaThunderbird-45.5.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2061-1 Security update for MozillaFirefox, MozillaFirefox-branding-SLED, mozilla-nspr and mozilla-nss SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2016:2254-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2397-1 Security update for flex, at, bogofilter, cyrus-imapd, kdelibs4, libQtWebKit4, libbonobo, mdbtools, netpbm, openslp, sgmltool, virtuoso, libqt5-qtwebkit SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2131-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2016:2195-1 Security update for MozillaFirefox SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2016:2253-1 Security update for MozillaThunderbird SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:14572-1 firefox-esr-128.5.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10071-1 MozillaFirefox-50.1.0-1.1 on GA media SUSE / openSUSE Security Updates · May 7, 2025
References
- [oss-security] 20160718 CVE request: flex: Buffer overflow in generated code (yy_get_next_buffer) mailing-list
- [oss-security] 20160726 Re: CVE request: flex: Buffer overflow in generated code (yy_get_next_buffer) mailing-list
- https://github.com/westes/flex/commit/a5cbe929ac3255d371e698f62dc256afe7006466
- DSA-3653 vendor-advisory
- GLSA-201701-31 vendor-advisory