CVE-2026-30803 Overview
CVE-2026-30803 is an integer underflow vulnerability [CWE-191] in the Core Libraries of RTI Connext Micro. The flaw affects Connext Micro versions from 4.0.0 before 4.3.0. An attacker can trigger an integer wraparound that causes the library to overread adjacent buffer memory. The vulnerability is reachable over the network without authentication or user interaction. Successful exploitation can disclose sensitive memory contents and disrupt the availability of services that depend on the Data Distribution Service (DDS) middleware. Connext Micro is widely deployed in embedded and real-time systems, including industrial control, robotics, and autonomous platforms.
Critical Impact
Remote, unauthenticated attackers can induce buffer overreads in RTI Connext Micro, potentially leaking memory contents and impacting service availability across DDS-connected systems.
Affected Products
- RTI Connext Micro Core Libraries 4.0.0 through versions before 4.3.0
- Embedded systems and applications linking the affected Connext Micro libraries
- DDS-based distributed applications using vulnerable middleware builds
Discovery Timeline
- 2026-06-17 - CVE-2026-30803 published to the National Vulnerability Database (NVD)
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2026-30803
Vulnerability Analysis
The vulnerability is an integer underflow, classified under [CWE-191], in the Connext Micro Core Libraries. When a numeric value used to compute a buffer offset or length is decremented below zero, the unsigned arithmetic wraps to a very large positive value. The library then uses this wrapped value as a size or index when reading from a buffer. The result is an out-of-bounds read that exposes memory contents the caller should not access. Because Connext Micro processes data received from remote DDS participants, an attacker with network reachability to a vulnerable endpoint can supply crafted messages that drive the underflow condition.
Root Cause
The root cause is missing or incorrect validation of numeric inputs used in size or length calculations within the Core Libraries. A length field or counter is decremented or subtracted without verifying that the result remains within expected bounds. The wrapped value is then trusted by downstream parsing routines, leading to a buffer overread.
Attack Vector
The attack vector is network-based and requires no privileges or user interaction. An attacker sends a crafted DDS protocol message to a Connext Micro participant. The malformed length or counter field triggers the underflow during message parsing. The vulnerable routine then reads beyond the intended buffer boundary, exposing process memory in subsequent processing or returned content.
No public proof-of-concept exploit is available at the time of publication. Refer to the RTI Vulnerability advisory for CVE-2026-30803 for vendor-supplied technical details.
Detection Methods for CVE-2026-30803
Indicators of Compromise
- Malformed DDS-RTPS protocol messages with length or counter fields that would underflow when decremented
- Unexpected process crashes, segmentation faults, or memory access violations in applications linked against Connext Micro 4.0.0 to 4.2.x
- Anomalous outbound responses from DDS participants containing unexpected memory fragments
Detection Strategies
- Inventory all software using RTI Connext Micro Core Libraries and identify versions in the affected range 4.0.0 through 4.2.x
- Inspect DDS traffic for protocol messages with inconsistent length fields, particularly values that decrement to negative or zero with attached payload data
- Correlate application crash telemetry with network events involving DDS endpoints to identify exploitation attempts
Monitoring Recommendations
- Enable verbose logging in DDS participants to capture malformed message events and parsing errors
- Monitor network segments carrying DDS-RTPS traffic for unexpected sources or volumes targeting embedded systems
- Track process memory and crash dumps from systems running Connext Micro to detect overread-induced instability
How to Mitigate CVE-2026-30803
Immediate Actions Required
- Upgrade RTI Connext Micro Core Libraries to version 4.3.0 or later in all affected applications and devices
- Restrict network reachability to DDS participants using firewalls, segmentation, or VLAN isolation
- Audit deployed firmware and embedded applications to confirm the linked Connext Micro version
Patch Information
RTI has addressed the issue in Connext Micro 4.3.0. Consult the RTI Vulnerability advisory for CVE-2026-30803 for upgrade instructions and any vendor-supplied backport guidance. Rebuild and redeploy all applications that statically link the Core Libraries after upgrading.
Workarounds
- Limit DDS communication to trusted networks and authenticated participants where the DDS Security plugins are supported
- Apply network access control lists to block untrusted hosts from reaching DDS discovery and user traffic ports
- Disable or isolate Connext Micro endpoints that do not require external connectivity until patching is complete
# Example: restrict DDS-RTPS discovery and user traffic to a trusted subnet
# Default RTPS ports are in the 7400-7500 range (domain dependent)
iptables -A INPUT -p udp --dport 7400:7500 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 7400:7500 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
