# CVE-2021-31378: Denial of service in Junos OS > Attackers can cause broadband subscribers to get stuck in a Terminating state via spoofed RADIUS messages, denying network access. - **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/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:** 19 Oct 2021 - **Updated:** 16 Sep 2024 - **Also known as:** GHSA-8pcm-vgvx-r5p5 ## What is CVE-2021-31378? CVE-2021-31378 is a medium-severity denial of service vulnerability in Juniper Junos, published on 19 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description In broadband environments, including but not limited to Enhanced Subscriber Management, (CHAP, PPP, DHCP, etc.), on Juniper Networks Junos OS devices where RADIUS servers are configured for managing subscriber access and a subscriber is logged in and then requests to logout, the subscriber may be forced into a "Terminating" state by an attacker who is able to send spoofed messages appearing to originate from trusted RADIUS server(s) destined to the device in response to the subscriber's request. These spoofed messages cause the Junos OS General Authentication Service (authd) daemon to force the broadband subscriber into this "Terminating" state which the subscriber will not recover from thereby causing a Denial of Service (DoS) to the endpoint device. Once in the "Terminating" state, the endpoint subscriber will no longer be able to access the network. Restarting the authd daemon on the Junos OS device will temporarily clear the subscribers out of the "Terminating" state. As long as the attacker continues to send these spoofed packets and subscribers request to be logged out, the subscribers will be returned to the "Terminating" state thereby creating a persistent Denial of Service to the subscriber. An indicator of compromise may be seen by displaying the output of "show subscribers summary". The presence of subscribers in the "Terminating" state may indicate the issue is occurring. This issue affects: Juniper Networks Junos OS 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S8, 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R1-S7, 19.2R3-S3; 19.3 versions prior to 19.3R2-S6, 19.3R3-S3; 19.4 versions prior to 19.4R1-S4, 19.4R1-S4, 19.4R3-S3; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R3-S1; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2. This issue does not affect: Juniper Networks Junos OS 12.3 version 12.3R1 and later versions; 15.1 version 15.1R1 and later versions. Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime) ## Which versions are affected by CVE-2021-31378? It affects 1 product. Products: Juniper Junos. ## How do I fix CVE-2021-31378? No fix has been published for CVE-2021-31378 yet. Limit exposure of the affected software until one is available. ## Is CVE-2021-31378 being exploited? There is no known exploitation of CVE-2021-31378 in the wild and no public exploit code. ## Other vulnerabilities in Juniper Junos - [CVE-2023-36845](https://insights.sbomify.com/CVE-2023-36845/): Juniper Junos OS EX Series and SRX Series PHP External Variable Modification (critical 9.8, exploited in the wild) - [CVE-2020-1631](https://insights.sbomify.com/CVE-2020-1631/): Juniper Junos OS Path Traversal (high 8.8, exploited in the wild) - [CVE-2025-21590](https://insights.sbomify.com/CVE-2025-21590/): Juniper Junos OS Improper Isolation or Compartmentalization (medium 6.7, exploited in the wild) - [CVE-2023-36851](https://insights.sbomify.com/CVE-2023-36851/): Juniper Junos OS SRX Series Missing Authentication for Critical Function (medium 5.3, exploited in the wild) - [CVE-2023-36844](https://insights.sbomify.com/CVE-2023-36844/): Juniper Junos OS EX Series PHP External Variable Modification (medium 5.3, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-31378 and fix it if it is affected. What it is: CVE-2021-31378 is a medium-severity denial of service vulnerability in Juniper Junos, published on 19 Oct 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-2021-31378 in the wild and no public exploit code. Affected product: Juniper Junos. 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-2021-31378/ (Markdown: https://insights.sbomify.com/CVE-2021-31378/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31378 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31378 - OSV: https://osv.dev/vulnerability/CVE-2021-31378 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-31378/ Summaries are generated and may contain mistakes; the official description above is the record.