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snap7 CVE-2026-51218

| EUVDEUVD-2026-40244 MEDIUM
Heap-based Buffer Overflow (CWE-122)
2026-06-29 mitre GHSA-6m46-rpq9-jh59
Heap Overflow Denial Of Service Buffer Overflow N A
6.5
CVSS 3.1 · Vendor: mitre
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Severity by source

Vendor (mitre) PRIMARY
6.5 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
vuln.today AI
7.5 HIGH

Server-side packet processing crash requires no user interaction; UI:R in provided vector is inconsistent with the described mechanism and appears to be a scoring error.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (mitre).

CVSS VectorVendor: mitre

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

3
Analysis Generated
Jun 30, 2026 - 14:24 vuln.today
CVSS changed
Jun 30, 2026 - 14:22 NVD
6.5 (MEDIUM)
CVE Published
Jun 29, 2026 - 00:00 cve.org
UNKNOWN (no severity yet)

DescriptionCVE.org

A heap buffer overflow in the TS7Worker::PerformFunctionWrite() function (/core/s7_server.cpp) of snap7 v1.4.3 allows attackers to cause a Denial of Service (DoS) via a crafted packet.

AnalysisAI

Heap buffer overflow in snap7 v1.4.3 crashes the embedded S7 server when processing a specially crafted write function packet targeting TS7Worker::PerformFunctionWrite() in /core/s7_server.cpp. Systems deploying snap7 as an S7-compatible communication server - common in industrial SCADA, HMI, and IoT gateway applications bridging to Siemens S7-series PLCs - can be disrupted remotely with no privileges required per the CVSS PR:N designation. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Recon
Identify host with snap7 server port exposed (TCP 102)
Delivery
Establish TCP connection to S7 server
Exploit
Craft malformed S7 write function packet
Install
Send packet to TS7Worker::PerformFunctionWrite()
C2
Trigger heap buffer overflow
Execute
Crash snap7 server process
Impact
Disrupt PLC communication and dependent SCADA/HMI systems
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Vulnerability AssessmentAI

Exploitation The target host must be running snap7 v1.4.3 with the snap7 server component active and the S7 server port (typically TCP 102) reachable by the attacker. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The provided CVSS score of 6.5 uses the vector AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H, but the UI:R (User Interaction Required) designation is inconsistent with the described attack mechanism: a server passively receiving a crafted network packet does not require any user interaction to trigger a crash. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker with network access to TCP port 102 on a host running snap7 v1.4.3 in server mode sends a specially crafted S7 write function request. The malformed packet triggers a heap buffer overflow in TS7Worker::PerformFunctionWrite(), corrupting heap memory and crashing the server process. …
Remediation No vendor-released patch has been identified at time of analysis. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-51218 vulnerability details – vuln.today
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