# CVE-2026-115723: Snap7 out-of-bounds write in passive partner

Source: https://junglewise.ai/threats/cve-2026-115723-snap7-through-1-4-3-contains-an-out-of-bounds-write  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-115723 · Severity: high · CVSS 7.4 · Published 2026-10-23

Snap7 is an industrial communication library used in SCADA, HMI, and gateway systems to connect to Siemens PLCs. A malicious PLC or peer device can crash these industrial processes or corrupt their memory by sending specially crafted messages that bypass buffer validation, potentially disrupting critical infrastructure operations.

## Quick answers

**Is CVE-2026-115723 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-115723 being exploited in the wild.

**How severe is CVE-2026-115723?** High severity, with a CVSS score of 7.4, published 23 October 2026.

**Which products and versions are affected?** Snap7 through 1.4.3.

**Is there a fix for CVE-2026-115723?** 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-2026-115723 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-115723?** Check whether you run Snap7 at an affected version. 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

The passive partner in Snap7 through 1.4.3 fails to validate the BSend total length declared by an active peer, allowing the attacker to declare up to 65535 bytes while sending truncated fragments. A BRecv memcpy operation then writes past the allocated buffer boundary, triggering an out-of-bounds write. The vulnerability requires the attacker to connect from a configured peer address and can result in process crash or memory corruption.

## Affected products

- Snap7 through 1.4.3

## Timeline

- 2026-10-23: disclosed

## References

- [https://github.com/davenardella/snap7/blob/30f37da3114024a71ba93f7fd855c680b97a406f/src/core/s7_partner.cpp](https://github.com/davenardella/snap7/blob/30f37da3114024a71ba93f7fd855c680b97a406f/src/core/s7_partner.cpp)
- [https://github.com/davenardella/snap7/blob/30f37da3114024a71ba93f7fd855c680b97a406f/src/core/s7_partner.cpp](https://github.com/davenardella/snap7/blob/30f37da3114024a71ba93f7fd855c680b97a406f/src/core/s7_partner.cpp)