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CVE-2026-8836 is a remotely exploitable stack-based buffer overflow in lwIP up to and including version 2.2.1. The flaw is located in the SNMPv3 USM handler, specifically in the function snmp_parse_inbound_frame within src/apps/snmp/snmp_msg.c. Improper handling of the msgAuthenticationParameters field during inbound SNMPv3 message parsing can cause a stack buffer to be overwritten, leading to memory corruption. Because the vulnerable code processes network-supplied input, an attacker can trigger the condition remotely by sending a crafted SNMPv3 packet to a device or application using the affected lwIP component.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a small standalone Python proof-of-concept for CVE-2026-8836 affecting lwIP SNMPv3. It contains three files: a README describing the vulnerability and usage, an empty requirements.txt, and a single executable script, exploit.py, which is the main entry point. The exploit is not part of a larger framework. The Python script implements a minimal ASN.1/BER encoder to build a syntactically valid SNMPv3 message. Its core capability is constructing a malicious SNMPv3 packet whose USM security parameters contain an oversized msgAuthenticationParameters OCTET STRING. The vulnerable target is expected to copy this attacker-controlled field into a fixed 12-byte stack buffer, triggering a stack-based overflow. The packet wraps this field inside a normal-looking SNMPv3 GET request using OID 1.3.6.1.2.1.1.1.0 and sends it over UDP to a user-specified target and port. Operationally, the script supports: selecting target IP and UDP port, choosing overflow length, sending multiple packets with optional delay, and loading arbitrary overflow bytes from a local file. If no payload file is supplied, it fills the overflow region with repeated 0x41 bytes. This makes the exploit more than a pure crash tester, but it still remains a basic PoC rather than a fully weaponized exploit because it does not include target-specific ROP, shell delivery, or reliability logic. The main network target is the SNMP service on UDP/161. There are no hardcoded remote C2 endpoints or callbacks; the exploit is a one-way packet sender. The likely effect on a vulnerable device is denial of service via crash, with potential for code execution depending on target memory layout and any custom payload supplied by the operator.
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