CVE-2026-4736 Overview
CVE-2026-4736 is an Improper Handling of Values vulnerability [CWE-229] affecting the No-Chicken Echo-Mate project. The flaw resides in the SDK/rv1106-sdk/sysdrv/source/kernel/include/net/netfilter modules, specifically in the nf_tables.h, nft_byteorder.c, and nft_meta.c source files. The issue affects Echo-Mate versions before V250329. A local attacker with low privileges can leverage this flaw to compromise the confidentiality, integrity, and availability of the affected system and downstream components.
Critical Impact
A local, low-privileged attacker can exploit improper value handling in netfilter kernel modules to achieve high-impact compromise of the affected device and connected subsystems.
Affected Products
- No-Chicken Echo-Mate versions before V250329
- Echo-Mate SDK component: rv1106-sdk/sysdrv/source/kernel/include/net/netfilter
- Source files: nf_tables.h, nft_byteorder.c, nft_meta.c
Discovery Timeline
- 2026-03-24 - CVE-2026-4736 published to the National Vulnerability Database (NVD)
- 2026-04-30 - CVE-2026-4736 last updated in NVD
Technical Details for CVE-2026-4736
Vulnerability Analysis
The vulnerability stems from improper handling of values within the netfilter subsystem bundled in the Echo-Mate SDK for the Rockchip rv1106 platform. Netfilter components such as nft_byteorder.c perform byte-order conversion on register data, while nft_meta.c handles metadata extraction. Improper validation or normalization of these values [CWE-229] can lead to inconsistent kernel state when packets traverse nf_tables rules.
Because the affected files are kernel-resident netfilter components, exploitation operates inside the kernel boundary. An attacker with local access and low privileges can trigger malformed value processing through netfilter rule manipulation or crafted packet flows. Successful exploitation produces high confidentiality, integrity, and availability impact on the vulnerable system and propagates impact to subsequent components.
Root Cause
The root cause is improper handling of values [CWE-229] in netfilter table and metadata routines. The header nf_tables.h defines the data structures consumed by nft_byteorder.c and nft_meta.c. When these routines fail to validate or correctly interpret length, type, or register values, downstream kernel logic operates on attacker-influenced data without enforcing expected invariants.
Attack Vector
The attack vector is local. An authenticated user with low privileges interacts with the netfilter interface on the device. Exploitation requires high attack complexity and produces a vulnerable proof-of-concept condition reported in the upstream pull request. No verified public exploit code is available. See the GitHub Pull Request for the upstream fix and technical discussion.
Detection Methods for CVE-2026-4736
Indicators of Compromise
- Unexpected kernel log entries referencing nft_byteorder or nft_meta operations on affected Echo-Mate devices
- Unauthorized nf_tables rule additions or modifications by low-privileged accounts
- Kernel panics, oopses, or netfilter subsystem instability on devices running Echo-Mate firmware prior to V250329
Detection Strategies
- Inventory all Echo-Mate devices and identify firmware versions older than V250329 for prioritized remediation
- Audit local user accounts and capabilities that permit interaction with nf_tables on affected devices
- Compare deployed netfilter module hashes against known-good baselines built from patched SDK sources
Monitoring Recommendations
- Collect kernel ring buffer (dmesg) output centrally and alert on netfilter-related faults
- Log nft command invocations and netlink activity targeting netfilter subsystems
- Monitor for repeated process crashes or privilege transitions on embedded rv1106 devices
How to Mitigate CVE-2026-4736
Immediate Actions Required
- Upgrade No-Chicken Echo-Mate firmware to version V250329 or later
- Restrict local shell and netfilter administrative access to trusted users only
- Apply the upstream patch referenced in the GitHub Pull Request when rebuilding affected SDK images
Patch Information
The maintainers addressed the issue in Echo-Mate V250329. The fix is tracked in the upstream repository through the pull request linked above, which updates the affected netfilter source files nf_tables.h, nft_byteorder.c, and nft_meta.c. Operators rebuilding from SDK source should integrate the upstream changes and redeploy device firmware.
Workarounds
- Disable or remove unused nf_tables rulesets on affected devices until firmware is updated
- Enforce least-privilege user policies so non-administrative accounts cannot manipulate netfilter state
- Isolate vulnerable Echo-Mate devices on restricted network segments to limit local access exposure
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
