CVE-2020-28327

What it is

A res_pjsip_session crash was discovered in Asterisk Open Source 13.x before 13.37.1, 16.x before 16.14.1, 17.x before 17.8.1, and 18.x before 18.0.1. and Certified Asterisk before 16.8-cert5. Upon receiving a new SIP Invite, Asterisk did not return the created dialog locked or referenced. This caused a gap between the creation of the dialog object, and its next use by the thread that created it. Depending on some off-nominal circumstances and timing, it was possible for another thread to free said dialog in this gap. Asterisk could then crash when the dialog object, or any of its dependent objects, were dereferenced or accessed next by the initial-creation thread. Note, however, that this crash can only occur when using a connection-oriented protocol (e.g., TCP or TLS, but not UDP) for SIP transport. Also, the remote client must be authenticated, or Asterisk must be configured for anonymous calling.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of service disruption.

Exploit odds

1.9% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2020-11-06 19:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.9% in the next 30 days (EPSS).
• Severity: 5.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2020-11-06 19:15 UTC

Last modified

2026-06-17 03:10 UTC

Exploit probability

1.9% · EPSS, next 30 days

Weakness

CWE-404

Record status

Modified

Affected

• Digium Certified Asterisk 16.8
• Sangoma Asterisk < 13.37.1
• Sangoma Asterisk < 16.14.1
• Sangoma Asterisk < 17.8.1
• Sangoma Asterisk < 18.0.1

Attack profile CVSS 3.1 · 5.3

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2020-28327.md and follow it. Check whether this project is affected by CVE-2020-28327. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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