CVE-2018-6794

Description

Suricata before 4.0.4 is prone to an HTTP detection bypass vulnerability in detect.c and stream-tcp.c. If a malicious server breaks a normal TCP flow and sends data before the 3-way handshake is complete, then the data sent by the malicious server will be accepted by web clients such as a web browser or Linux CLI utilities, but ignored by Suricata IDS signatures. This mostly affects IDS signatures for the HTTP protocol and TCP stream content; signatures for TCP packets will inspect such network traffic as usual.

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	1:4.0.4-1	—
Debian 13	suricata	1:4.0.4-1	—
Debian 8	suricata	2.0.7-2+deb8u3	DLA-1603-1

Ubuntu

Security tracker ↗

Release	Package	Fixed in	Advisory
Ubuntu 18.04 LTS	suricata	No fix yet	—
Ubuntu 16.04 LTS	suricata	No fix yet	—

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

Exploit-DB 1

Suricata < 4.0.4 - IDS Detection Bypass EDB-44247 · dos · Mar 5, 2018

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Advisories 1

DLA-1603-1 suricata - security update Debian Security (DSA / DLA) · Mar 9, 2026

Suricata before 4.0.4 is prone to an HTTP detection bypass vulnerability in detect.c and stream-tcp.c. If a malicious server breaks a norma…