CVE-2021-45098Public exploitNetwork attack vector

HTTP signature evasion via crafted RST options

Published Dec 16, 2021 · Updated Nov 3, 2025

Detection evasion in OISF Suricata before 6.0.4 allows remote attackers to bypass HTTP signatures with a crafted TCP RST packet. Suricata's TCP stream engine accepts an RST bearing an unvalidated MD5 or TCP-AO option and closes its tracked session even when the endpoint rejects the packet. Inline IPS mode is required; subsequent forbidden HTTP traffic remains uninspected and avoids the configured reject action.

CVSS severity7.5
High
EPSS probability1.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Detection evasion in OISF Suricata before 6.0.4 allows remote attackers to bypass HTTP signatures with a crafted TCP RST packet. Suricata's TCP stream engine accepts an RST bearing an unvalidated MD5 or TCP-AO option and closes its tracked session even when the endpoint rejects the packet. Inline IPS mode is required; subsequent forbidden HTTP traffic remains uninspected and avoids the configured reject action.

The record

CVE
CVE-2021-45098
Published
Dec 16, 2021
Updated
Nov 3, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1562.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record 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

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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

T1562.001Impair Defenses: Disable or Modify Tools

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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