Description
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.
References10
- github.com/asterisk/asterisk/commit/0e89514084490070c5ecee419ec…
- github.com/asterisk/asterisk/commit/647b35c3cfd4a2cc3b1fb7560b0…
- github.com/asterisk/asterisk/commit/7a1ffcdf38cc76d1c4eae516516…
- github.com/asterisk/asterisk/commit/b4be3bd67ce4ac35b94fbfa860c…
- github.com/asterisk/asterisk/commit/b5281828dad7d44658439ba6393…
- github.com/asterisk/asterisk/commit/dca516f6d895e8867d48fa56b6c…
- github.com/asterisk/asterisk/commit/ee1b66a5e40733ba0b9fad7fc4d…
- github.com/asterisk/asterisk/releases/tag/20.20.1
- github.com/asterisk/asterisk/releases/tag/21.12.3
- github.com/asterisk/asterisk/releases/tag/22.10.1
Metrics
- CVSS 4.0
-
8.2
HIGH
Score source: CNA
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 1% percentile: 48 · as of 3 November 2026
- CWE
- CWE-120CWE-787
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.