# CVE-2026-57191: Asterisk buffer overflow in MWI NOTIFY parser

Source: https://junglewise.ai/threats/cve-2026-57191-asterisk-is-an-open-source-private-branch-exchange-and-telephony  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-57191 · Severity: info · Published 2026-10-27

Asterisk is a telecommunications server that processes phone calls and messaging. An unauthenticated attacker can send a specially crafted SIP message that causes a buffer overflow, permanently disabling all telephone functionality until the server is manually restarted. This allows an attacker to take down phone systems without authentication.

Technologies: [Asterisk Project Asterisk](https://junglewise.ai/threats/technologies/asterisk-project-asterisk), [Asterisk Project Certified Asterisk](https://junglewise.ai/threats/technologies/asterisk-project-certified-asterisk). Vendors: [Asterisk Project](https://junglewise.ai/threats/vendors/asterisk-project).

## Quick answers

**Is CVE-2026-57191 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-57191 being exploited in the wild.

**How severe is CVE-2026-57191?** Informational severity, published 27 October 2026.

**Which products and versions are affected?** Asterisk Project Asterisk before 20.20.1, 21.12.3, 22.10.1, 23.4.1; Asterisk Project Certified Asterisk before 20.7-cert11, 22.8-cert3.

**Is there a fix for CVE-2026-57191?** Yes: fixed in Asterisk 20.20.1, 21.12.3, 22.10.1, 23.4.1; Certified Asterisk 20.7-cert11, 22.8-cert3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-57191 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-57191?** Check whether you run Asterisk Project Asterisk or Asterisk Project Certified Asterisk at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Asterisk 20.20.1, 21.12.3, 22.10.1, 23.4.1; Certified Asterisk 20.7-cert11, 22.8-cert3

## Technical details

An unbounded sscanf in res_pjsip_pubsub parses the Message-Account field from incoming SIP MWI NOTIFY messages into a 512-byte stack buffer. An unauthenticated attacker can send a NOTIFY with a Message-Account value exceeding 512 bytes, causing a stack buffer overflow that corrupts the PJSIP transport layer. The transport becomes permanently disabled without crashing the process, requiring a manual Asterisk restart to restore SIP functionality.

## Affected products

- Asterisk Project Asterisk before 20.20.1, 21.12.3, 22.10.1, 23.4.1
- Asterisk Project Certified Asterisk before 20.7-cert11, 22.8-cert3

## Timeline

- 2026-10-27: disclosed

## References

- [https://github.com/asterisk/asterisk/commit/0e89514084490070c5ecee419ec5ee37b7c49528](https://github.com/asterisk/asterisk/commit/0e89514084490070c5ecee419ec5ee37b7c49528)
- [https://github.com/asterisk/asterisk/commit/647b35c3cfd4a2cc3b1fb7560b085feba5c24b4b](https://github.com/asterisk/asterisk/commit/647b35c3cfd4a2cc3b1fb7560b085feba5c24b4b)

## Related threats

- [Asterisk SMS buffer overflow in app_sms](https://junglewise.ai/threats/cve-2026-57199-asterisk-is-an-open-source-private-branch-exchange-and-telephony)
- [Asterisk heap buffer overflow in Codec2 decoder](https://junglewise.ai/threats/cve-2026-57192-asterisk-is-an-open-source-private-branch-exchange-and-telephony)
- [Asterisk SQL injection in CEL event logging](https://junglewise.ai/threats/cve-2026-57190-asterisk-is-an-open-source-private-branch-exchange-and-telephony)
- [Asterisk buffer over-read in PJSIP MWI parser](https://junglewise.ai/threats/cve-2026-57185-asterisk-is-an-open-source-private-branch-exchange-and-telephony)
- [Asterisk heap-use-after-free in PJSIP TCP/SDP handling](https://junglewise.ai/threats/cve-2026-57187-asterisk-is-an-open-source-private-branch-exchange-and-telephony)