CVE-2021-1501Network attack vector

Device reload via SIP pinhole hash lookup

Published Apr 29, 2021 · Updated Nov 8, 2024

Denial of service in Cisco ASA Software allows remote attackers to crash and reload affected devices with crafted SIP traffic. The SIP inspection engine crashes while performing a hash lookup for a SIP pinhole connection derived from transit traffic. SIP inspection must be configured and is enabled by default; exploitation interrupts device service during the reload.

CVSS severity8.6
High
EPSS probability1.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco ASA Software allows remote attackers to crash and reload affected devices with crafted SIP traffic. The SIP inspection engine crashes while performing a hash lookup for a SIP pinhole connection derived from transit traffic. SIP inspection must be configured and is enabled by default; exploitation interrupts device service during the reload.

The record

CVE
CVE-2021-1501
Published
Apr 29, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco Adaptive Security Appliance (ASA) Software
Classifications
CWE-613, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Adaptive Security Appliance (ASA) Softwareversion=n/a

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.8NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:C
8.6Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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