Algorithm Downgrade in pjsip - #VU146533
Published: August 31, 2026
Vulnerability identifier: #VU146533
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-757
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to downgrade subsequent in-dialog requests to plaintext.
The vulnerability exists due to selection of less-secure transport during negotiation in the dialog layer target refresh handling in pjsip_dlg_on_rx_request() and pjsip_dlg_on_rx_response() in sip_dialog.c when processing a Contact URI from an in-dialog target refresh. A remote attacker can supply a non-sips Contact to downgrade subsequent in-dialog requests to plaintext.
Only applications using SIPS-secured dialogs are affected.
Affected software
pjsip
Remediation
Install security update from vendor's website.
pjsip - update to 2.18