CVE-2024-53703 Overview
CVE-2024-53703 is a stack-based buffer overflow [CWE-121] in the mod_httprp library loaded by the Apache web server on SonicWall SMA100 SSLVPN appliances. The flaw affects firmware version 10.2.1.13-72sv and earlier. Remote, unauthenticated attackers can trigger the overflow over the network and potentially achieve arbitrary code execution on the appliance. SonicWall SMA100 series devices provide secure remote access to enterprise networks, making them high-value targets for initial access operations.
Critical Impact
Successful exploitation can corrupt the Apache worker process stack and lead to remote code execution on internet-facing SSLVPN appliances, granting attackers a foothold at the network perimeter.
Affected Products
- SonicWall SMA 200 and SMA 210 appliances running firmware 10.2.1.13-72sv and earlier
- SonicWall SMA 400 and SMA 410 appliances running firmware 10.2.1.13-72sv and earlier
- SonicWall SMA 500v virtual appliance running firmware 10.2.1.13-72sv and earlier
Discovery Timeline
- 2024-12-05 - CVE-2024-53703 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-53703
Vulnerability Analysis
The vulnerability resides in mod_httprp, a SonicWall-specific Apache module loaded by the SMA100 web server that handles HTTP request processing for the SSLVPN portal. Attackers send a crafted HTTP request to the SSLVPN interface, and mod_httprp writes attacker-controlled data past the bounds of a stack-allocated buffer.
Stack-based buffer overflows of this class can overwrite saved return addresses, frame pointers, and stack canaries that protect the Apache worker. When exploitation succeeds, the attacker redirects execution flow to attacker-supplied shellcode or to existing code gadgets using return-oriented programming (ROP). Because the SSLVPN portal must be reachable from the internet to provide its function, exposed appliances are directly reachable by unauthenticated attackers.
The EPSS score of 12.713% places this issue in the 95th percentile, indicating elevated likelihood of exploitation activity relative to the broader CVE population.
Root Cause
The root cause is missing bounds checking when mod_httprp copies request-derived data into a fixed-size stack buffer. The Apache module trusts the length or structure of an attacker-controlled HTTP field and performs an unsafe copy operation, classifying it under [CWE-121] Stack-based Buffer Overflow.
Attack Vector
The attack vector is network-based and requires no authentication or user interaction. An attacker sends a specially crafted HTTPS request to the SSLVPN service exposed by the SMA100 appliance. The attack complexity is rated High because reliable code execution depends on bypassing stack protections and address-space layout randomization on the target firmware build.
The vulnerability is described in prose only because no public proof-of-concept exploit code has been released. Refer to the SonicWall PSIRT advisory SNWLID-2024-0018 for vendor technical details.
Detection Methods for CVE-2024-53703
Indicators of Compromise
- Unexpected Apache worker process crashes or segmentation faults recorded in SMA100 system logs around inbound SSLVPN requests
- Outbound connections from the appliance to unfamiliar IP addresses, particularly shortly after anomalous HTTP requests
- New or modified files in writable paths on the appliance, or unexplained changes to configuration after public-facing requests
Detection Strategies
- Inspect HTTPS traffic to SMA100 SSLVPN endpoints for overly long headers, malformed request lines, or unusual binary content that does not match legitimate VPN client behavior
- Correlate Apache error logs with subsequent process restarts on the appliance to identify exploitation attempts that trigger crashes
- Compare firmware version banners returned by management interfaces against the patched releases to identify unpatched assets
Monitoring Recommendations
- Forward SMA100 syslog and Apache logs to a centralized SIEM and alert on repeated worker termination events tied to a single source IP
- Monitor network egress from the appliance management plane for any connection that does not match SonicWall update or licensing infrastructure
- Track authentication events on the SSLVPN portal for anomalous post-exploitation sessions originating from internal-looking source addresses
How to Mitigate CVE-2024-53703
Immediate Actions Required
- Upgrade SMA100 firmware to a release later than 10.2.1.13-72sv as identified in SonicWall PSIRT SNWLID-2024-0018
- Restrict access to the SSLVPN management and portal interfaces to known source networks until patching is complete
- Review appliance logs and authentication records for signs of prior exploitation before returning the device to normal operation
Patch Information
SonicWall has released fixed firmware for the SMA 200, 210, 400, 410, and 500v product lines. Administrators should consult SonicWall PSIRT SNWLID-2024-0018 for the exact fixed versions and download links, then apply updates following SonicWall's documented upgrade procedure.
Workarounds
- Disable the SSLVPN service on affected appliances until firmware can be updated if business operations allow
- Place the SMA100 appliance behind an external web application firewall that can drop oversized or malformed HTTP requests targeting the SSLVPN endpoint
- Enforce geographic and source IP allowlists on the SSLVPN interface to reduce the attack surface available to unauthenticated remote attackers
# Configuration example: restrict SSLVPN access at an upstream firewall
# Replace 203.0.113.0/24 with your authorized client networks
iptables -A FORWARD -p tcp -d <sma100-ip> --dport 443 \
-s 203.0.113.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <sma100-ip> --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
