# CVE-2026-16225: davenardella snap7 out-of-bounds write in TSnap7Peer::NegotiatePDULength

Source: https://junglewise.ai/threats/cve-2026-16225-davenardella-snap7-out-of-bounds-write-in-tsnap7peer  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-19. Updated: 2026-07-19  
License: CC BY 4.0 with a link back

CVE-2026-16225 · Severity: medium · CVSS 6.3 · Published 2026-07-19

Snap7 is an open-source communication library used to connect software applications with Siemens S7 PLCs (Industrial Controllers). A security flaw allows a malicious server or a network attacker to send a specially crafted message that causes the Snap7 client to crash or corrupt its own memory. This could lead to a denial of service for industrial monitoring systems or potentially allow for further unauthorized actions on the system running the Snap7 client.

## Quick answers

**Is CVE-2026-16225 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-16225 being exploited in the wild.

**How severe is CVE-2026-16225?** Medium severity, with a CVSS score of 6.3, published 19 July 2026.

**Which products and versions are affected?** davenardella snap7 up to 1.4.3.

**Is there a fix for CVE-2026-16225?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-16225 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-16225?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A client-side intra-object heap overflow exists in davenardella snap7 up to version 1.4.3. The vulnerability is rooted in TSnap7Peer::NegotiatePDULength within src/core/s7_peer.cpp, where the library fails to enforce an upper bound on the PDULength negotiated with a server. An attacker-controlled server can provide an excessively large PDULength, which is subsequently used by TSnap7MicroClient::opWriteArea() to calculate buffer offsets for a memcpy operation. This results in an out-of-bounds write when the client attempts to assemble a local request buffer, leading to heap corruption or a process crash. The exploit is public and requires the attacker to either control the server or intercept the network traffic (man-in-the-middle).

## Affected products

- davenardella snap7 up to 1.4.3

## Timeline

- 2026-07-19: disclosed: Initial disclosure via VulDB and NVD
- 2026-07-19: advisory

## References

- [https://github.com/davenardella/snap7/](https://github.com/davenardella/snap7/)
- [https://github.com/davenardella/snap7/issues/17](https://github.com/davenardella/snap7/issues/17)
- [https://vuldb.com/cve/CVE-2026-16225](https://vuldb.com/cve/CVE-2026-16225)
- [https://vuldb.com/submit/858228](https://vuldb.com/submit/858228)
- [https://vuldb.com/vuln/380047](https://vuldb.com/vuln/380047)
- [https://vuldb.com/vuln/380047/cti](https://vuldb.com/vuln/380047/cti)