# CVE-2020-15567: Race condition in n/a > A race condition in Xen's Intel EPT handling allows guest users to cause privilege escalation or denial of service on vulnerable compiler builds. - **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 7 Jul 2020 - **Updated:** 4 Aug 2024 - **Also known as:** ALPINE-CVE-2020-15567, DEBIAN-CVE-2020-15567, GHSA-mpwm-7x8j-q5j2, UBUNTU-CVE-2020-15567 ## What is CVE-2020-15567? CVE-2020-15567 is a high-severity vulnerability in Debian Debian Linux, published on 7 Jul 2020. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description An issue was discovered in Xen through 4.13.x, allowing Intel guest OS users to gain privileges or cause a denial of service because of non-atomic modification of a live EPT PTE. When mapping guest EPT (nested paging) tables, Xen would in some circumstances use a series of non-atomic bitfield writes. Depending on the compiler version and optimisation flags, Xen might expose a dangerous partially written PTE to the hardware, which an attacker might be able to race to exploit. A guest administrator or perhaps even an unprivileged guest user might be able to cause denial of service, data corruption, or privilege escalation. Only systems using Intel CPUs are vulnerable. Systems using AMD CPUs, and Arm systems, are not vulnerable. Only systems using nested paging (hap, aka nested paging, aka in this case Intel EPT) are vulnerable. Only HVM and PVH guests can exploit the vulnerability. The presence and scope of the vulnerability depends on the precise optimisations performed by the compiler used to build Xen. If the compiler generates (a) a single 64-bit write, or (b) a series of read-modify-write operations in the same order as the source code, the hypervisor is not vulnerable. For example, in one test build using GCC 8.3 with normal settings, the compiler generated multiple (unlocked) read-modify-write operations in source-code order, which did not constitute a vulnerability. We have not been able to survey compilers; consequently we cannot say which compiler(s) might produce vulnerable code (with which code-generation options). The source code clearly violates the C rules, and thus should be considered vulnerable. Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) ## Which versions are affected by CVE-2020-15567? It affects 4 products. Products: Debian Debian Linux, Fedoraproject Fedora, Opensuse Leap, Xen Xen. ## How do I fix CVE-2020-15567? Apply the vendor's patch. ## Is CVE-2020-15567 being exploited? There is no known exploitation of CVE-2020-15567 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2020-15567 and fix it if it is affected. What it is: CVE-2020-15567 is a high-severity vulnerability in Debian Debian Linux, published on 7 Jul 2020. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2020-15567 in the wild and no public exploit code. Affected product: Debian Debian Linux. 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-2020-15567/ (Markdown: https://insights.sbomify.com/CVE-2020-15567/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-15567 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-15567 - OSV: https://osv.dev/vulnerability/CVE-2020-15567 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-15567/ Summaries are generated and may contain mistakes; the official description above is the record.