CVE-2026-20221

mediumpriority · track · 23EPSS 0.006 · 47 %ileNLUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.58% (47th) EPSS
CVSS 5.8 · medium
Is it mine?
780 products
Check your exposure
Who says so?
2 sources
cisco_csaf · ncsc_nl

EPSS · scored 2026-10-27

Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine. This vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

02

cvss

Technical severity, 0–10. One row per scoring source.

5.8
010

base score 0–10 · higher = more severe · hover a vector to decode

v3.15.8mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Lprimary · psirt@cisco.com USexploitability 3.9 · impact 1.4
v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L/E:Usecondary · CVSS-BT (t0sche)
v3.15.8mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Lsecondary · NCSC-NL NL
v3.15.8mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:Lsecondary · Cisco PSIRT US
03

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS
04

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-476USCWE-476USCWE-476US
05

affected products (780)

Products and version ranges known to be affected.

showing 20 of 780
06

advisories (2)

Vendor and ecosystem advisories describing this.

  • NCSC-2026-0450Kwetsbaarheden verholpen in Snort 3 van CiscoNL2026-10-22csaf · ncsc_nlNL

    Cisco heeft meerdere kwetsbaarheden verholpen in Snort 3, het open source intrusion detection en prevention systeem dat in diverse Cisco-producten wordt gebruikt.

  • cisco-sa-snort3-gre-JNpMHrTvMultiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerability2026-10-21csaf · cisco_csafUS

    Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine. This vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the Details ["#details"] section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is part of a group of advisories. For a complete list of the advisories and links to them, see Cisco Advance Notification for Publication of October 21, 2026, Security Advisories ["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-notice-QGwHnJ6k"]. In addition, for further documentation of improvements and fixes in Open Source Snort 3, see Multiple Cisco Products Snort 3 Security Hardening Release: October 2026 ["https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-snort3-ybgmhTQe"].

07

sources

Which sources assert this record, and when.

cisco_csafncsc_nlNVDCVE.orgMITRE
published 2026-10-21modified 2026-10-22
08

references (1) nvd

External citations — patches, advisories, analysis.

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