Description
An issue was discovered in Suricata 5.0.0. It is possible to bypass/evade any tcp based signature by overlapping a TCP segment with a fake FIN packet. The fake FIN packet is injected just before the PUSH ACK packet we want to bypass. The PUSH ACK packet (containing the data) will be ignored by Suricata because it overlaps the FIN packet (the sequence and ack number are identical in the two packets). The client will ignore the fake FIN packet because the ACK flag is not set. Both linux and windows clients are ignoring the injected packet.
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 | suricata | 1:5.0.2-1 | — |
| Debian 13 | suricata | 1:5.0.2-1 | — |
| Debian 8 | suricata | 2.0.7-2+deb8u5 | DLA-2087-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | suricata | No fix yet | — |
| Ubuntu 16.04 LTS | suricata | No fix yet | — |
Advisories 1
- DLA-2087-1 suricata - security update Debian Security (DSA / DLA) · Mar 9, 2026
References
- https://redmine.openinfosecfoundation.org/issues/3324
- https://github.com/OISF/suricata/commit/fa692df37a796c3330c81988d15ef1a219afc006
- https://redmine.openinfosecfoundation.org/issues/3394
- https://github.com/OISF/suricata/commit/1c63d3905852f746ccde7e2585600b2199cefb4b
- [debian-lts-announce] 20200130 [SECURITY] [DLA 2087-1] suricata security update mailing-list