# CVE-2021-28701: Race condition in xen > A race condition in Xen grant table handling allows guests to retain access to freed memory pages, potentially leading to information disclosure or privilege escalation. - **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:** 8 Sep 2021 - **Updated:** 3 Aug 2024 - **Also known as:** ALPINE-CVE-2021-28701, DEBIAN-CVE-2021-28701, GHSA-423x-f92f-r5fm, SUSE-SU-2021:3140-1, SUSE-SU-2021:3140-2, SUSE-SU-2021:3141-1, SUSE-SU-2021:3181-1, SUSE-SU-2021:3213-1, UBUNTU-CVE-2021-28701, openSUSE-SU-2021:1301-1, openSUSE-SU-2021:3140-1 ## What is CVE-2021-28701? CVE-2021-28701 is a high-severity vulnerability in Debian Debian Linux, published on 8 Sep 2021. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, are de-allocated when a guest switches (back) from v2 to v1. Freeing such pages requires that the hypervisor enforce that no parallel request can result in the addition of a mapping of such a page to a guest. That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes. Unfortunately, when XSA-379 was being prepared, this similar issue was not noticed. Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) ## Which versions are affected by CVE-2021-28701? It affects 3 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `xen` | SUSE:HPE Helion OpenStack 8 | All versions | 4.9.4_22-3.94.2 | | `xen` | SUSE:Linux Enterprise Micro 5.0 | All versions | 4.13.3_04-3.37.1 | | `xen` | SUSE:Linux Enterprise Micro 5.1 | All versions | 4.14.2_06-3.12.1 | | `xen` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 4.13.3_04-3.37.1 | | `xen` | SUSE:Linux Enterprise Module for Basesystem 15 SP3 | All versions | 4.14.2_06-3.12.1 | | `xen` | SUSE:Linux Enterprise Module for Server Applications 15 SP2 | All versions | 4.13.3_04-3.37.1 | | `xen` | SUSE:Linux Enterprise Module for Server Applications 15 SP3 | All versions | 4.14.2_06-3.12.1 | | `xen` | SUSE:Linux Enterprise Server 12 SP3-BCL | All versions | 4.9.4_22-3.94.2 | | `xen` | SUSE:Linux Enterprise Server 12 SP3-LTSS | All versions | 4.9.4_22-3.94.2 | | `xen` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 4.12.4_14-3.52.1 | | `xen` | SUSE:Linux Enterprise Server for SAP Applications 12 SP3 | All versions | 4.9.4_22-3.94.2 | | `xen` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 4.12.4_14-3.52.1 | | `xen` | SUSE:Linux Enterprise Software Development Kit 12 SP5 | All versions | 4.12.4_14-3.52.1 | | `xen` | SUSE:OpenStack Cloud 8 | All versions | 4.9.4_22-3.94.2 | | `xen` | SUSE:OpenStack Cloud Crowbar 8 | All versions | 4.9.4_22-3.94.2 | | `xen` | openSUSE:Leap 15.2 | All versions | 4.13.3_04-lp152.2.30.1 | | `xen` | openSUSE:Leap 15.3 | All versions | 4.14.2_06-3.12.1 | Products: Debian Debian Linux, Fedoraproject Fedora, Xen Xen. ## How do I fix CVE-2021-28701? Apply the vendor's patch. ## Is CVE-2021-28701 being exploited? There is no known exploitation of CVE-2021-28701 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-2021-28701 and fix it if it is affected. What it is: CVE-2021-28701 is a high-severity vulnerability in Debian Debian Linux, published on 8 Sep 2021. 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-2021-28701 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-2021-28701/ (Markdown: https://insights.sbomify.com/CVE-2021-28701/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28701 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28701 - OSV: https://osv.dev/vulnerability/CVE-2021-28701 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-28701/ Summaries are generated and may contain mistakes; the official description above is the record.