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CVE Record

CVE-2021-45098: An issue was discovered in Suricata before 6.0.4.

An issue was discovered in Suricata before 6.0.4. It is possible to bypass/evade any HTTP-based signature by faking an RST TCP packet with random TCP options of the md5header from the client side. After the three-way handshake, it's possible to inject an RST ACK with a random TCP md5header option. Then, the client can send an HTTP GET request with a forbidden URL. The server will ignore the RST ACK and send the response HTTP packet for the client's request. These packets will not trigger a Suricata reject action.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Suricata versions before 6.0.4 could miss or fail to reject certain HTTP traffic when a client sends a crafted TCP reset pattern. The business risk is reduced visibility or enforcement for web-based threats, not direct compromise of Suricata itself.

Executive priority

Treat this as a monitoring and enforcement gap. Prioritize remediation where Suricata is used to block or detect web threats on important network paths, but current sources do not support emergency active-exploitation handling.

Technical view

The CVE describes an evasion where a client-side RST ACK with random TCP MD5 header options after handshake can cause Suricata HTTP signatures and reject actions to be bypassed while the server still responds to the HTTP request.

Likely exposure

Organizations using Suricata before 6.0.4 for HTTP inspection, alerting, or reject actions are the likely exposure. Evidence does not identify specific appliances, distributions, or deployments beyond Suricata.

Exploitation context

The source bundle does not show KEV listing or confirmed active exploitation. The description does describe a bypass technique, so assume motivated researchers or attackers could understand the class of evasion from public information.

Researcher notes

The key research point is TCP stream handling around RST ACK packets carrying random MD5 header options. Public evidence is limited to the CVE description, OISF references, a fixing commit, releases, and a Debian advisory.

Mitigation direction

  • Upgrade Suricata to 6.0.4 or later, or vendor-confirmed fixed packages.
  • Check OISF release notes and distribution advisories for supported fixed versions.
  • Prioritize sensors enforcing HTTP reject actions or high-value perimeter inspection.
  • Avoid relying solely on HTTP signatures for critical blocking decisions.
  • Monitor vendor guidance for any additional operational mitigations.

Validation and detection

  • Inventory all Suricata sensors and record installed versions.
  • Confirm each deployment is 6.0.4 or later, or distribution-patched.
  • Review whether HTTP-based reject signatures are used for enforcement.
  • Run approved regression tests for HTTP detection and reject behavior.
  • Check change records for Debian or other backported package fixes.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2021-45098 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
6Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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