Asterisk Asterisk/Certified Asterisk Pubsub res_pjsip_pubsub sscanf Message-Account stack-based overflow

Summaryinfo

A vulnerability was found in Asterisk Asterisk and Certified Asterisk. It has been classified as very critical. This impacts the function sscanf of the file res_pjsip_pubsub of the component Pubsub. This manipulation of the argument Message-Account causes stack-based overflow. The identification of this vulnerability is CVE-2026-57191. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Asterisk Asterisk and Certified Asterisk (unknown version). It has been declared as very critical. Affected by this vulnerability is the function sscanf of the file res_pjsip_pubsub of the component Pubsub. The manipulation of the argument Message-Account with an unknown input leads to a stack-based overflow vulnerability. The CWE definition for the vulnerability is CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Asterisk is an open source private branch exchange and telephony toolkit. Prior to Asterisk 20.20.1, 21.12.3, 22.10.1, 23.4.1 and Certified Asterisk 20.7-cert11, 22.8-cert3, an unbounded `sscanf` in `res_pjsip_pubsub` when parsing the `MWI NOTIFY` `Message-Account` field may allow an unauthenticated attacker to send a carefully crafted packet that causes a stack buffer overflow and corrupts the underlying transport, permanently disabling all SIP functionality. An Asterisk restart is required to restore full operation. This issue is fixed in Asterisk 20.20.1, 21.12.3, 22.10.1, 23.4.1 and Certified Asterisk 20.7-cert11, 22.8-cert3.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-57191 since 06/24/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/27/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Communications System

Vendor

• Asterisk

Name

• Asterisk
• Certified Asterisk

Website

• Product: https://github.com/asterisk/asterisk/

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