CVE-2026-0791: ALGO 8180 IP Audio Alerter RCE Flaw

CVE-2026-0791 Overview

CVE-2026-0791 is a stack-based buffer overflow vulnerability affecting ALGO 8180 IP Audio Alerter devices. This vulnerability allows remote attackers to execute arbitrary code on affected installations without requiring authentication. The flaw exists within the handling of the Replaces header in SIP INVITE requests, where user-supplied data is copied to a fixed-length stack-based buffer without proper validation of the input length.

Critical Impact

Unauthenticated remote attackers can achieve arbitrary code execution on vulnerable ALGO 8180 IP Audio Alerter devices by sending malicious SIP INVITE requests with crafted Replaces headers, potentially leading to complete device compromise.

Affected Products

• ALGO 8180 IP Audio Alerter

Discovery Timeline

• 2026-01-23 - CVE-2026-0791 published to NVD
• 2026-01-26 - Last updated in NVD database

Technical Details for CVE-2026-0791

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The flaw resides in the SIP protocol handling component of the ALGO 8180 IP Audio Alerter device. When processing incoming SIP INVITE requests, the device parses the Replaces header without adequately validating the length of the supplied data before copying it to a fixed-length buffer allocated on the stack.

The vulnerability is network-accessible but requires high attack complexity to exploit successfully. No authentication or user interaction is required, making it particularly dangerous for devices exposed to untrusted networks. Successful exploitation allows an attacker to execute code in the context of the device, potentially gaining full control over the affected system.

This vulnerability was tracked as ZDI-CAN-28300 and disclosed through the Zero Day Initiative program as ZDI-26-013.

Root Cause

The root cause of this vulnerability is the lack of proper input validation when handling the Replaces header in SIP INVITE requests. The device copies user-controlled data directly into a stack-based buffer without checking whether the input exceeds the buffer's allocated size. This missing bounds check allows an attacker to overflow the buffer and overwrite adjacent stack memory, including return addresses and saved frame pointers.

Attack Vector

The attack is conducted over the network by sending specially crafted SIP INVITE requests to the target device. The attacker constructs a malicious Replaces header containing data that exceeds the expected buffer size. When the vulnerable device processes this request, the oversized data overwrites critical stack structures, enabling the attacker to redirect program execution to attacker-controlled code.

The vulnerability manifests during the parsing of SIP INVITE requests containing the Replaces header. When the header value exceeds the fixed-length buffer allocation, adjacent stack memory is corrupted, potentially allowing control flow hijacking. For detailed technical analysis, refer to the Zero Day Initiative Advisory ZDI-26-013.

Detection Methods for CVE-2026-0791

Indicators of Compromise

• Unusual or malformed SIP INVITE requests targeting ALGO 8180 devices with abnormally long Replaces header values
• Device crashes, unexpected reboots, or abnormal behavior following SIP traffic
• Evidence of unauthorized code execution or persistence mechanisms on affected devices
• Network traffic showing repeated SIP INVITE requests from suspicious sources

Detection Strategies

• Deploy network intrusion detection rules to identify SIP INVITE requests with excessively long Replaces headers
• Monitor SIP traffic for malformed or anomalous packets targeting ALGO 8180 devices
• Implement deep packet inspection for SIP protocol traffic to detect potential exploitation attempts
• Analyze device logs for signs of crashes or unexpected restarts coinciding with SIP activity

Monitoring Recommendations

• Enable comprehensive logging on network devices handling SIP traffic
• Configure alerts for SIP traffic anomalies and potential buffer overflow exploitation patterns
• Regularly review network traffic patterns to and from ALGO 8180 IP Audio Alerter devices
• Monitor device health metrics for signs of compromise or instability

How to Mitigate CVE-2026-0791

Immediate Actions Required

• Isolate ALGO 8180 IP Audio Alerter devices from untrusted networks where possible
• Implement network segmentation to limit exposure of vulnerable devices
• Deploy firewall rules to restrict SIP traffic to trusted sources only
• Monitor for vendor security updates and apply patches when available

Patch Information

No vendor patch information is currently available. Monitor the Zero Day Initiative Advisory and ALGO vendor communications for updates on remediation guidance.

Workarounds

• Restrict network access to ALGO 8180 devices using firewall rules or VLANs
• Limit SIP traffic to known and trusted IP addresses and networks
• Consider disabling SIP functionality if not operationally required until a patch is available
• Implement network-level filtering to block SIP requests with unusually long headers

# Example firewall rule to restrict SIP access to trusted networks only
# Adjust IP ranges according to your environment
iptables -A INPUT -p udp --dport 5060 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p udp --dport 5060 -j DROP
iptables -A INPUT -p tcp --dport 5060 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 5060 -j DROP