What is the CVSS score of CVE-2021-32558?

CVE-2021-32558 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 9.1%.

Is there a public PoC exploit available for CVE-2021-32558?

Yes, a public proof-of-concept exploit is available for CVE-2021-32558. Prioritise patching immediately. EPSS: 9.1%.

Is there a patch available for CVE-2021-32558?

Yes, a patch is available for CVE-2021-32558. Update the affected software to the latest version immediately.

Asterisk CVE-2021-32558

HIGH

Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection') (CWE-74)

2021-07-30 cve@mitre.org

Denial Of Service Debian Debian Linux Asterisk Certified Asterisk Digium

7.5

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-74 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Input neutralization, injection prevention
Impact	CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the high-severity affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 9.1% exploitation probability (EPSS)

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AnalysisAI

An issue was discovered in Sangoma Asterisk 13.x before 13.38.3, 16.x before 16.19.1, 17.x before 17.9.4, and 18.x before 18.5.1, and Certified Asterisk before 16.8-cert10. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-74. An issue was discovered in Sangoma Asterisk 13.x before 13.38.3, 16.x before 16.19.1, 17.x before 17.9.4, and 18.x before 18.5.1, and Certified Asterisk before 16.8-cert10. If the IAX2 channel driver receives a packet that contains an unsupported media format, a crash can occur. Affected products include: Digium Asterisk, Digium Certified Asterisk, Debian Debian Linux. Version information: before 13.38.3.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

DescriptionNVD

An issue was discovered in Sangoma Asterisk 13.x before 13.38.3, 16.x before 16.19.1, 17.x before 17.9.4, and 18.x before 18.5.1, and Certified Asterisk before 16.8-cert10. If the IAX2 channel driver receives a packet that contains an unsupported media format, a crash can occur.

Threat Intelligence Overview

EPSS Score

9.1%

Top 5% exploitable

Exploit

POC

Public exploit code exists

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 9.1%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +9

CVSS: +38

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)NVD

cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:-:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc1:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc2:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc3:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc4:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert2:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert3:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert4:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc1:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc2:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc3:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc4:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert5:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert6:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert7:*:*:*:*:*:*

cpe:2.3:a:digium:certified_asterisk:16.8:cert8:*:*:*:*:*:*

+ 3 more

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References

Advisories & patches

PATCH http://packetstormsecurity.com/files/163639/Asterisk-Project-Security-Advisory-AST-2021-008.html PATCH http://seclists.org/fulldisclosure/2021/Jul/49 PATCH https://downloads.asterisk.org/pub/security/AST-2021-008.html REF https://lists.debian.org/debian-lts-announce/2021/08/msg00005.html REF https://www.debian.org/security/2021/dsa-4999

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