CVE-2026-57166: CWE-121: Stack-based Buffer Overflow in pjsip pjproject

PJSIP's pjproject library contained a stack-based buffer overflow (CWE-121) in its PJLIB-UTIL telnet CLI front-end before commit 4472a31. Multiple command-line handling paths write attacker-controlled data into fixed-size stack buffers without proper bounds checking, allowing a long command line to overflow these buffers during command-line feedback rendering. This vulnerability affects only applications that enable the telnet CLI front-end (e.g., via pj_cli_telnet_create() or --cli-telnet-port). The telnet CLI is unauthenticated, so any client able to connect can issue arbitrary CLI commands. The overflow may cause application termination. The vulnerability has been fixed by the referenced commit.

The vulnerability can cause application termination due to stack buffer overflow when processing a malformed or overly long command line in the telnet CLI front-end. Since the telnet CLI is unauthenticated, any client with network access to this interface can trigger the overflow. However, because exploitation requires prior access to the unauthenticated CLI, the impact is limited to denial of service or potential application crash within that context. No further privilege escalation or remote code execution is indicated.

This vulnerability has been patched in pjproject via commit 4472a31. Users should update to a version including this commit to remediate the issue. Applications that do not enable the telnet CLI front-end are not affected. If the telnet CLI is enabled, disabling it can mitigate exposure. No additional mitigation is required beyond applying the official fix.