CVE-2026-41416: Teluu Pjsip Buffer Overflow Vulnerability

CVE-2026-41416 Overview

CVE-2026-41416 is an integer overflow vulnerability affecting PJSIP, a free and open source multimedia communication library written in C. The vulnerability exists in versions 2.16 and earlier when processing Session Description Protocol (SDP) messages with asymmetric ptime configuration. An integer overflow occurs during media stream buffer size calculation, which can result in an undersized buffer allocation. This condition can lead to unexpected application termination or memory corruption, potentially enabling attackers to compromise VoIP and multimedia communication systems.

Critical Impact
Network-accessible integer overflow vulnerability in PJSIP media stream handling can cause denial of service or memory corruption in VoIP applications.

Affected Products

Teluu PJSIP versions 2.16 and earlier
Applications and VoIP systems built on vulnerable PJSIP library versions
SIP-based communication platforms utilizing PJSIP for media handling

Discovery Timeline

2026-04-24 - CVE-2026-41416 published to NVD
2026-04-28 - Last updated in NVD database

Technical Details for CVE-2026-41416

Vulnerability Analysis

This vulnerability is classified as an Integer Overflow (CWE-190). The flaw resides in PJSIP's media stream handling code, specifically in the buffer size calculation logic that processes SDP (Session Description Protocol) messages. When an SDP message contains asymmetric ptime (packet time) configuration values, the library performs arithmetic operations to calculate the required buffer size for media stream processing.

The integer overflow occurs because the calculation does not properly validate or constrain the input values before performing multiplication or addition operations. When specially crafted ptime values are processed, the resulting buffer size calculation wraps around, producing a value much smaller than required. The subsequent buffer allocation uses this incorrect (undersized) value, creating a mismatch between the allocated memory and the actual data that will be written to it.

This condition can manifest in two primary ways: immediate application crash due to memory access violations, or more concerning, memory corruption that could potentially be leveraged for further exploitation. Given that PJSIP is widely used in VoIP applications, IP-PBX systems, and communication platforms, this vulnerability has significant implications for enterprise communication infrastructure.

Root Cause

The root cause is insufficient validation of ptime configuration values in SDP processing combined with unsafe integer arithmetic during buffer size calculation. When asymmetric ptime values are specified in an SDP message, the multiplication or addition operations used to compute the buffer size can exceed the maximum value representable by the integer type, causing a wrap-around to a small positive number. This results in allocation of an undersized buffer that cannot accommodate the actual media stream data.

Attack Vector

The attack can be executed remotely over the network without authentication. An attacker can craft a malicious SDP message containing specially designed asymmetric ptime values and send it to a target system running vulnerable PJSIP-based applications. When the target processes this SDP during session negotiation (such as during a SIP INVITE or re-INVITE), the integer overflow is triggered.

The attack mechanism involves sending a crafted SDP offer or answer containing asymmetric ptime attributes that, when processed by the media stream initialization code, cause the buffer size calculation to overflow. This results in a heap buffer being allocated with insufficient size, leading to out-of-bounds writes when media data is subsequently processed.

For technical details on the vulnerability mechanism and the fix applied, refer to the GitHub Security Advisory GHSA-f33g-8hjq-62xr.

Detection Methods for CVE-2026-41416

Indicators of Compromise

Unexpected crashes or terminations of PJSIP-based applications during SIP session negotiation
Abnormal SDP messages containing unusual or extreme ptime attribute values in SIP traffic
Memory corruption indicators such as heap corruption errors in application logs
Unusual SIP INVITE or re-INVITE requests with malformed media descriptions

Detection Strategies

Monitor SIP traffic for SDP messages with asymmetric or unusually large ptime values that could trigger integer overflow conditions
Implement application-level logging to capture SDP parsing events and flag anomalous ptime configurations
Deploy intrusion detection signatures to identify malformed SDP payloads targeting PJSIP implementations
Use memory analysis tools to detect heap corruption patterns indicative of exploitation attempts

Monitoring Recommendations

Enable verbose logging on SIP proxies and VoIP gateways to capture full SDP content during session negotiations
Implement network-based monitoring at SIP ingress points to detect anomalous media attribute values
Configure crash reporting and core dump analysis for rapid identification of exploitation attempts
Monitor system stability metrics for PJSIP-dependent services to detect denial of service conditions

How to Mitigate CVE-2026-41416

Immediate Actions Required

Upgrade all PJSIP installations to version 2.17 or later, which contains the security fix
Audit all applications and systems that depend on PJSIP library to identify vulnerable deployments
Review SIP infrastructure to identify exposed endpoints running vulnerable PJSIP versions
Implement network segmentation to limit exposure of VoIP systems to untrusted networks

Patch Information

Teluu has addressed this vulnerability in PJSIP version 2.17. The fix is available in the GitHub commit 66fe416c96e957417621b7be16e9e587d159f9bb. Organizations should upgrade to the patched version immediately.

For complete details about the vulnerability and remediation, see the GitHub Security Advisory GHSA-f33g-8hjq-62xr.

Workarounds

Deploy SIP-aware firewalls or session border controllers (SBCs) to filter and validate SDP content before reaching PJSIP applications
Implement input validation at the SIP proxy level to reject SDP messages with extreme ptime values
Restrict network access to VoIP systems to trusted IP ranges to reduce attack surface
Consider temporary isolation of vulnerable PJSIP applications until patching can be completed

bash

# Verify PJSIP version in your installation
pjsua --version

# After upgrading, confirm the patched version
# Ensure version shows 2.17 or higher