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Vulnerabilities

Vulnerability · CVE-2026-20043

ZDI-26-867: Cisco Snort sf_unfold_header Out-Of-Bounds Write Remote Code Execution Vulnerability

Published Oct 21, 2026 · catalog updated Oct 22, 2026 · ZDI-26-867: Cisco Snort sf_unfold_header

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-20043. EPSS is 0.36%. Act only if a listed version of ZDI-26-867: Cisco Snort sf_unfold_header is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (ZDI-26-867: Cisco Snort sf_unfold_header).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.36%
Remediation
Advisory link
Affected products
See sources for product scope

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco owned Open Source Snort 3 Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20043 are related to issues concerning out-of-bounds writes that are grouped under the Common Weakness Enumeration (CWE) Base CWE-787.

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-20043

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-20043. EPSS is 0.36%. Act only if a listed version of ZDI-26-867: Cisco Snort sf_unfold_header is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-787: Out-of-bounds Write. EPSS 0.36%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 21, 2026 · NIST NVD

    Detected

    As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco owned Open Source Snort 3 Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20043 are related to issues concerning out-of-bo

  2. Oct 22, 2026 · NIST NVD

    Updated

    As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco owned Open Source Snort 3 Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20043 are related to issues concerning out-of-bo

Sources

  • Cisco Security AdvisoriesVendor advisoryCVE-2026-20043

    As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco owned Open Source Snort 3 Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple in

    sec.cloudapps.cisco.com
  • CVE.orgVulnerability recordCVE-2026-20043

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-20043

    30-day exploitation probability 0.36%

    first.org
  • NIST NVDVulnerability recordCVE-2026-20043

    As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco owned Open Source Snort 3 Software engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple interna

    nvd.nist.gov
  • Zero Day InitiativeCoordinated disclosureZDI-26-867

    This vulnerability allows remote attackers to execute arbitrary code on affected installations of Cisco Snort. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 9.8. The following CVEs are assigned: CVE-2026-20043.

    zerodayinitiative.com

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • Cisco Security AdvisoriesNov 6, 2026
  • Zero Day InitiativeNov 4, 2026
  • NIST NVDOct 22, 2026
  • CVE.orgOct 21, 2026