CVE-2026-16225
Received Received - Intake

Out-of-Bounds Write in Snap7 Library

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: VulDB

Description
A security flaw has been discovered in davenardella snap7 up to 1.4.3. The impacted element is the function TSnap7Peer::NegotiatePDULength of the file src/core/s7_peer.cpp. The manipulation of the argument PDULength results in out-of-bounds write. The attack can be executed remotely. The exploit has been released to the public and may be used for attacks.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-19
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-16225
EUVD
EUVD-2026-45435

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
davenardella snap7 to 1.4.3 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-119 The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
CWE-787 The product writes data past the end, or before the beginning, of the intended buffer.

Attack-Flow Graph

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Executive Summary

CVE-2026-16225 is a client-side heap overflow in the Snap7 library affecting versions up to 1.4.3. The vulnerability occurs in the TSnap7Peer::NegotiatePDULength function where a malicious server can manipulate the PDULength argument during S7 PDU negotiation. This leads to an out-of-bounds write when the client later processes a WriteArea request, as it uses the unvalidated PDULength to compute data size for a memcpy operation. The overflow corrupts the client's heap object state.

Detection Guidance

To detect this vulnerability, monitor network traffic for abnormal S7 PDU negotiation attempts where PDULength exceeds standard bounds (typically 4096 bytes). Inspect logs for crashes or heap corruption in applications using Snap7 library versions up to 1.4.3. Use tools like Wireshark to analyze Siemens S7 protocol traffic for unusually large PDU sizes.

Impact Analysis

This vulnerability allows remote attackers to cause denial of service, heap corruption, and undefined behavior on systems using vulnerable Snap7 versions. Since Snap7 is a communication library for Siemens S7 PLCs, affected systems could experience crashes or instability when interacting with malicious servers. The exploit can be triggered through normal API usage like TS7Client::WriteArea().

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by enabling remote denial of service, heap corruption, and undefined behavior in systems using the Snap7 library. Such disruptions may lead to unauthorized access or data breaches, which are critical concerns under these regulations.

Mitigation Strategies

Immediately update Snap7 to the latest version beyond 1.4.3 where the vulnerability is patched. If updating is not possible, implement network-level controls to block malformed S7 PDU negotiation packets. Restrict access to systems using Snap7 to trusted networks only.

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