Description
OpenVPN, when using a 64-bit block cipher, makes it easier for remote attackers to obtain cleartext data via a birthday attack against a long-duration encrypted session, as demonstrated by an HTTP-over-OpenVPN session using Blowfish in CBC mode, aka a "Sweet32" attack.
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.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | openvpn | 2.3.10-1ubuntu2.1 | USN-3339-1 |
| Ubuntu 14.04 LTS | openvpn | 2.3.2-7ubuntu3.2 | USN-3339-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | openvpn | 2.3.8-16.14.1 | SUSE-SU-2017:1622-1 |
| SLES 11 SP4 | openvpn | 2.0.9-143.47.3.1 | SUSE-SU-2017:2838-1 |
| SLES 11 SP3 | openvpn | 2.0.9-143.47.3.1 | SUSE-SU-2017:2838-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP2 | openvpn | 2.3.8-16.14.1 | SUSE-SU-2017:1622-1 |
| SLES for SAP 11 SP4 | openvpn | 2.0.9-143.47.3.1 | SUSE-SU-2017:2838-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | openvpn | 2.0.9-143.47.3.1 | SUSE-SU-2017:2838-1 |
Advisories 4
- USN-3339-1 openvpn vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- SUSE-SU-2017:2838-1 Security update for openvpn SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2017:1622-1 Security update for openvpn SUSE / openSUSE Security Updates · Feb 4, 2026
- ICSA-19-192-04 ICSA-19-192-04 Siemens SIMATIC RF6XXR CISA ICS & IT advisories · Jul 9, 2019
References
- https://sweet32.info/
- https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05369403
- 1036695 vdb-entry
- http://www-01.ibm.com/support/docview.wss?uid=swg21995039
- http://www-01.ibm.com/support/docview.wss?uid=swg21991482
- GLSA-201611-02 vendor-advisory
- https://community.openvpn.net/openvpn/wiki/SWEET32
- http://www-01.ibm.com/support/docview.wss?uid=nas8N1021697
- 92631 vdb-entry
- https://cert-portal.siemens.com/productcert/pdf/ssa-556833.pdf