CVE-2026-57165: PJSIP: Pre-authentication overflow in the telnet CLI history
PJSIP is a free and open source multimedia communication library written in C. Prior to commit 628b716, a stack buffer overflow exists in the PJLIB-UTIL telnet CLI front-end when redrawing the command line during history recall (handleupdown() in clitelnet.c). This affects only applications that enable the telnet CLI front-end (same gating as the related CLI issue). The line-redraw sequence for a recalled history entry can accumulate more data than a fixed-size stack buffer holds, which may lead to application termination. Exploitation requires access to the unauthenticated telnet CLI, which already permits arbitrary CLI commands, so the additional impact is limited. Applications that do not enable the telnet CLI front-end are not affected. This issue has been patched via commit 628b716.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
PJSIP (PJLIB-UTIL telnet CLI front-end)to a version that resolves this vulnerability.Patch 628b716
Event History
Frequently Asked Questions
Which deployments are affected?
Only applications that enable the PJLIB-UTIL telnet CLI front-end are affected. Applications that do not enable that front-end are not affected.
What access does an attacker need?
An attacker needs access to the unauthenticated telnet CLI and must trigger command-line redrawing while recalling history entries. That telnet CLI already permits arbitrary CLI commands to anyone with access.
What is the likely impact?
The overflow may terminate the application. The advisory notes that the additional impact is limited because the required unauthenticated telnet CLI access already grants arbitrary CLI command execution.
What should teams do if they cannot immediately apply the fix?
Disable the telnet CLI front-end or prevent access to the unauthenticated telnet CLI. The issue is fixed by commit 628b716.