# CVE-2021-31340: Denial of service in SIMATIC RF166C > An attacker can cause a Denial-of-Service condition on Siemens SIMATIC RFID readers by sending a large number of incoming connections. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 8 Jun 2021 - **Updated:** 3 Aug 2024 - **Also known as:** GHSA-hjxf-6qxm-x8qg ## What is CVE-2021-31340? CVE-2021-31340 is a high-severity denial of service vulnerability in Siemens SIMATIC RF166C, published on 8 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description A vulnerability has been identified in SIMATIC RF166C (All versions > V1.1 and < V1.3.2), SIMATIC RF185C (All versions > V1.1 and < V1.3.2), SIMATIC RF186C (All versions > V1.1 and < V1.3.2), SIMATIC RF186CI (All versions > V1.1 and < V1.3.2), SIMATIC RF188C (All versions > V1.1 and < V1.3.2), SIMATIC RF188CI (All versions > V1.1 and < V1.3.2), SIMATIC RF360R (All versions < V2.0), SIMATIC Reader RF610R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF610R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF610R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF615R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF615R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF615R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF650R ARIB (All versions > V3.0 < V4.0), SIMATIC Reader RF650R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF650R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF650R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF680R ARIB (All versions > V3.0 < V4.0), SIMATIC Reader RF680R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF680R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF680R FCC (All versions > V3.0 < V4.0), SIMATIC Reader RF685R ARIB (All versions > V3.0 < V4.0), SIMATIC Reader RF685R CMIIT (All versions > V3.0 < V4.0), SIMATIC Reader RF685R ETSI (All versions > V3.0 < V4.0), SIMATIC Reader RF685R FCC (All versions > V3.0 < V4.0). Affected devices do not properly handle large numbers of incoming connections. An attacker may leverage this to cause a Denial-of-Service situation. Weakness: CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2021-31340? It affects 25 products. Products: Siemens Simatic Reader Rf610r Cmiit Firmware, Siemens Simatic Reader Rf610r Etsi Firmware, Siemens Simatic Reader Rf610r Fcc Firmware, Siemens Simatic Reader Rf615r Cmiit Firmware, Siemens Simatic Reader Rf615r Etsi Firmware, Siemens Simatic Reader Rf615r Fcc Firmware, Siemens Simatic Reader Rf650r Arib Firmware, Siemens Simatic Reader Rf650r Cmiit Firmware, Siemens Simatic Reader Rf650r Etsi Firmware, Siemens Simatic Reader Rf650r Fcc Firmware, Siemens Simatic Reader Rf680r Arib Firmware, Siemens Simatic Reader Rf680r Cmiit Firmware, Siemens Simatic Reader Rf680r Etsi Firmware, Siemens Simatic Reader Rf680r Fcc Firmware, Siemens Simatic Reader Rf685r Arib Firmware, Siemens Simatic Reader Rf685r Cmiit Firmware, Siemens Simatic Reader Rf685r Etsi Firmware, Siemens Simatic Reader Rf685r Fcc Firmware, Siemens Simatic Rf166c Firmware, Siemens Simatic Rf185c Firmware and 5 more. ## How do I fix CVE-2021-31340? No fix has been published for CVE-2021-31340 yet. Limit exposure of the affected software until one is available. ## Is CVE-2021-31340 being exploited? There is no known exploitation of CVE-2021-31340 in the wild and no public exploit code. ## Other vulnerabilities in Siemens SIMATIC RF166C - [CVE-2024-37990](https://insights.sbomify.com/CVE-2024-37990/): Misconfiguration in SIMATIC RF1140R (high 7.0) - [CVE-2024-37993](https://insights.sbomify.com/CVE-2024-37993/): Missing authorization in SIMATIC RF1140R (medium 6.9) - [CVE-2024-37991](https://insights.sbomify.com/CVE-2024-37991/): Missing authorization in SIMATIC RF1140R (medium 6.0) - [CVE-2024-37992](https://insights.sbomify.com/CVE-2024-37992/): Denial of service in SIMATIC RF1140R (medium 5.9) - [CVE-2024-37994](https://insights.sbomify.com/CVE-2024-37994/): Information disclosure in SIMATIC RF1140R (medium 5.3) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-31340 and fix it if it is affected. What it is: CVE-2021-31340 is a high-severity denial of service vulnerability in Siemens SIMATIC RF166C, published on 8 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-31340 in the wild and no public exploit code. Affected product: Siemens SIMATIC RF166C. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-31340/ (Markdown: https://insights.sbomify.com/CVE-2021-31340/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31340 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31340 - OSV: https://osv.dev/vulnerability/CVE-2021-31340 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-31340/ Summaries are generated and may contain mistakes; the official description above is the record.