CVE-2021-1623Network attack vector

Authenticated service interruption via SNMP punt flooding

Published Sep 23, 2021 · Updated Nov 7, 2024

Resource exhaustion in Cisco IOS XE Software on cBR-8 routers allows remote authenticated users to interrupt service via SNMP requests. The SNMP punt path accepts valid IPv4 or IPv6 SNMPv2c or SNMPv3 requests without a dedicated rate limit, so a high request volume overwhelms the path. Exploitation requires an enabled SNMP server and valid community strings or credentials; the reported consequence is denial of service.

CVSS severity7.7
High
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Cisco IOS XE Software on cBR-8 routers allows remote authenticated users to interrupt service via SNMP requests. The SNMP punt path accepts valid IPv4 or IPv6 SNMPv2c or SNMPv3 requests without a dedicated rate limit, so a high request volume overwhelms the path. Exploitation requires an enabled SNMP server and valid community strings or credentials; the reported consequence is denial of service.

The record

CVE
CVE-2021-1623
Published
Sep 23, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco IOS XE Software
Classifications
CWE-399, T1498.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ClamAV · Cisco IOS XE Softwareversion=n/a

Published CVSS scores

7.7CiscoCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X

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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-399Resource Management Errors
T1498.001Direct Network Flood

Public exploit references

No public exploit references are available in this record.

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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