CVE-2019-18792Public exploitNetwork attack vector

TCP signature evasion via broken ACK handling

Published Jan 6, 2020 · Updated Aug 5, 2024

TCP signature evasion in OISF Suricata 4.1.5 and 5.0.0 allows remote attackers to conceal inspected payloads with crafted segments. The TCP stream handler accepts a segment whose acknowledgment field is nonzero while the ACK flag is unset, then treats a later PUSH-ACK segment with the same sequence and acknowledgment numbers as overlapping data. An unauthenticated server able to send traffic through the monitored path can hide matching payload content from Suricata while Linux and Windows clients accept the later segment.

CVSS severity9.1
Critical
EPSS probability2.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TCP signature evasion in OISF Suricata 4.1.5 and 5.0.0 allows remote attackers to conceal inspected payloads with crafted segments. The TCP stream handler accepts a segment whose acknowledgment field is nonzero while the ACK flag is unset, then treats a later PUSH-ACK segment with the same sequence and acknowledgment numbers as overlapping data. An unauthenticated server able to send traffic through the monitored path can hide matching payload content from Suricata while Linux and Windows clients accept the later segment.

The record

CVE
CVE-2019-18792
Published
Jan 6, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-436, T1562
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 6, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.4NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:P
9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-436Interpretation Conflict
T1562Impair Defenses

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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