Vulnerabilities > CVE-2019-18792 - Interpretation Conflict vulnerability in multiple products
Attack vector
NETWORK Attack complexity
LOW Privileges required
NONE Confidentiality impact
NONE Integrity impact
HIGH Availability impact
HIGH Summary
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.
Vulnerable Configurations
| Part | Description | Count |
|---|---|---|
| Application | 2 | |
| OS | 1 |
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- HTTP Request Splitting HTTP Request Splitting (also known as HTTP Request Smuggling) is an attack pattern where an attacker attempts to insert additional HTTP requests in the body of the original (enveloping) HTTP request in such a way that the browser interprets it as one request but the web server interprets it as two. There are several ways to perform HTTP request splitting attacks. One way is to include double Content-Length headers in the request to exploit the fact that the devices parsing the request may each use a different header. Another way is to submit an HTTP request with a "Transfer Encoding: chunked" in the request header set with setRequestHeader to allow a payload in the HTTP Request that can be considered as another HTTP Request by a subsequent parsing entity. A third way is to use the "Double CR in an HTTP header" technique. There are also a few less general techniques targeting specific parsing vulnerabilities in certain web servers.
- HTTP Response Smuggling An attacker injects content into a server response that is interpreted differently by intermediaries than it is by the target browser. To do this, it takes advantage of inconsistent or incorrect interpretations of the HTTP protocol by various applications. For example, it might use different block terminating characters (CR or LF alone), adding duplicate header fields that browsers interpret as belonging to separate responses, or other techniques. Consequences of this attack can include response-splitting, cross-site scripting, apparent defacement of targeted sites, cache poisoning, or similar actions.
- HTTP Request Smuggling HTTP Request Smuggling results from the discrepancies in parsing HTTP requests between HTTP entities such as web caching proxies or application firewalls. Entities such as web servers, web caching proxies, application firewalls or simple proxies often parse HTTP requests in slightly different ways. Under specific situations where there are two or more such entities in the path of the HTTP request, a specially crafted request is seen by two attacked entities as two different sets of requests. This allows certain requests to be smuggled through to a second entity without the first one realizing it.
Nessus
| NASL family | Debian Local Security Checks |
| NASL id | DEBIAN_DLA-2087.NASL |
| description | Two vulnerabilities have recently been discovered in the stream-tcp code of the intrusion detection and prevention tool Suricata. CVE-2019-18625 It was possible to bypass/evade any tcp based signature by faking a closed TCP session using an evil server. After the TCP SYN packet, it was possible to inject a RST ACK and a FIN ACK packet with a bad TCP Timestamp option. The client would have ignored the RST ACK and the FIN ACK packets because of the bad TCP Timestamp option. CVE-2019-18792 It was possible to bypass/evade any tcp based signature by overlapping a TCP segment with a fake FIN packet. The fake FIN packet had to be injected just before the PUSH ACK packet we wanted to bypass. The PUSH ACK packet (containing the data) would have been ignored by Suricata because it would have overlapped the FIN packet (the sequence and ack number are identical in the two packets). The client would have ignored the fake FIN packet because the ACK flag would not have been set. For Debian 8 |
| last seen | 2020-06-01 |
| modified | 2020-06-02 |
| plugin id | 133363 |
| published | 2020-01-31 |
| reporter | This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof. |
| source | https://www.tenable.com/plugins/nessus/133363 |
| title | Debian DLA-2087-1 : suricata security update |
| code | |
References
- https://github.com/OISF/suricata/commit/1c63d3905852f746ccde7e2585600b2199cefb4b
- https://redmine.openinfosecfoundation.org/issues/3324
- https://redmine.openinfosecfoundation.org/issues/3394
- https://github.com/OISF/suricata/commit/fa692df37a796c3330c81988d15ef1a219afc006
- https://lists.debian.org/debian-lts-announce/2020/01/msg00032.html