CVE-2026-20221

Read full description

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.

CVSS 5.8 (MEDIUM)

Attention and evidence

HYPE SCORE

0.6/10

REALITY · THREAT PRIORITY

2.0/10

General review priority; not probability

Evidence confidence: Insufficient evidence

Why this priority?

Technical severity: CVSS 5.8: +2.03
Fresh EPSS: 0.58%: +0.01

General review priority, not probability, victim count or asset-specific risk. A range covers missing CVSS/EPSS inputs within the current evidence state.

Sources: 4 documents and public datasets.

Hype components

Headline sample (25%)

0/100

Press, 30 days (60%)

10/100

Grounded branding (15%)

0/100

HYPE TOTAL6/100

Sources and documents

Cisco Security Advisory

Technical advisory · 22 Oct 2026, 19:03 · Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerability

Cisco Security Advisory

Press · 22 Oct 2026, 19:03 · Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerability

Cisco Security Advisory

Technical advisory · 21 Oct 2026, 16:09 · Cisco Advance Notification for Publication of October 21, 2026, Security Advisories

Cisco Security Advisory

Press · 21 Oct 2026, 16:09 · Cisco Advance Notification for Publication of October 21, 2026, Security Advisories

Score evolution

● Hype ● Reality

Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.

First record: hype 0.6 · reality 2.0 (2026-11-02 15:14). The curve appears once the score changes.

Public exploit evidence

Public exploit entries / repo candidates

Evidence context and dated references

Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs. Published 15 days ago. Exploitation evidence usually takes weeks to show up: a low reality score can mean there is no data yet, not that the flaw is mild.

Evidence in context

Confidence in exploitation evidence: Insufficient evidence
Priority basis: Exploitation in attacks unconfirmed; CVSS 5.8; EPSS 0.6%
Attention, last 30 days: 2 distinct story titles; 2 press documents; 1 publisher domains.
Technical potential: network access, no prior privileges, no user interaction.
Observed activity: No exploitation observation is recorded.
Known scale: Not quantified.
Evidence confidence basis: Insufficient evidence

Score evaluated: 2026-11-05 14:00:00.097835+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z

Source event timeline

First press mention

21 Oct 2026, 16:09

Published

21 Oct 2026, 16:12

Latest press mention

22 Oct 2026, 19:03

Score calculated

05 Nov 2026, 14:00