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Security #4504

closed

tcp: Evasion possibility on wrong/unexpected ACK value in crafted SYN packets

Added by Peter Manev over 3 years ago. Updated about 3 years ago.

Status:
Closed
Priority:
Normal
Assignee:
Eric Leblond
Target version:
7.0.0-beta1
Affected Versions:
Label:
Needs backport to 5.0, Needs backport to 6.0
CVE:
2021-35063
Git IDs:

0d81173d6e912f4be9e3e8f7593d779d8ffed52f
556570f7dd7f21f11cffda5ebcb72738a29cbb90
2c8c043185a4700b042d2154f5076f1c82e5394b

Severity:
CRITICAL
Disclosure Date:

Description

affected versions: all

Please see the pcap attached.
Basically it logs no HTTP even with midstream enabled.

The problem is the first packet right away as it has ACK value that we check and disregard the whole flow/session.But Windows and Linux accept those and everyone else it seems.

Please also see attached a test case(py file) and a patch by Eric.

The pcap can not be shared or made public except of the devs with access to this issue of course.

Files

Download all files
test-nozero-ack.py (403 Bytes) test-nozero-ack.py Peter Manev, 05/28/2021 10:02 AM
0001-stream-tcp-avoid-evasion-by-sending-crafted-SYN-pack.patch (1.78 KB) 0001-stream-tcp-avoid-evasion-by-sending-crafted-SYN-pack.patch Peter Manev, 05/28/2021 10:02 AM

Related issues 2 (0 open — 2 closed)

Copied to Suricata - Security #4512: Evasion possibility on wrong/unexpected ACK value in crafted SYN packetsClosedVictor JulienActions
Copied to Suricata - Security #4513: Evasion possibility on wrong/unexpected ACK value in crafted SYN packetsClosedJeff LucovskyActions
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