{"answers":{"affected":"It affects 4 products.","exploited":"There is no known exploitation of CVE-2019-18421 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2019-18421 is a high-severity vulnerability in Debian Debian Linux, published on 31 Oct 2019. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2019-18421 and fix it if it is affected.\n\nWhat it is: CVE-2019-18421 is a high-severity vulnerability in Debian Debian Linux, published on 31 Oct 2019. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2019-18421 in the wild and no public exploit code.\n\nAffected product: Debian Debian Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. 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.\n2. 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.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2019-18421/ (Markdown: https://insights.sbomify.com/CVE-2019-18421/index.md)","id":"CVE-2019-18421","markdown":"https://insights.sbomify.com/CVE-2019-18421/index.md","name":"CVE-2019-18421","record":{"aliases":["ALPINE-CVE-2019-18421","DEBIAN-CVE-2019-18421","GHSA-7g44-3rf3-p4xf","UBUNTU-CVE-2019-18421"],"analysis":{"component_type":"operating_system","fix_type":"patch","impacts":["privilege_escalation","code_execution"],"network_reachable":"yes","non_default_config":false,"product_category":"Xen hypervisor","requires_auth":"low_privilege","summary":"A malicious PV guest administrator can escalate privileges to the host OS by exploiting race conditions in Xen's pagetable promotion and demotion operations.","user_interaction":"not_required","vuln_class":"race_condition"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"mitre","cpe":[{"product":"debian_linux","vendor":"debian"},{"product":"fedora","vendor":"fedoraproject"},{"product":"leap","vendor":"opensuse"},{"product":"xen","vendor":"xen"}],"cvss":{"score":7.5,"severity":"high","source":"nvd","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[{"id":"CWE-362","name":"Concurrent Execution using Shared Resource with Improper Synchronization"}],"description":"An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be \"promoted\" before being used as a pagetable, and \"demoted\" before being used for any other type. Xen also allows for \"recursive\" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, and so on. These operations may take an arbitrarily large amount of time, and so must be re-startable. Unfortunately, making recursive pagetable promotion and demotion operations restartable is incredibly complicated, and the code contains several races which, if triggered, can cause Xen to drop or retain extra type counts, potentially allowing guests to get write access to in-use pagetables. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All x86 systems with untrusted PV guests are vulnerable. HVM and PVH guests cannot exercise this vulnerability.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"Race condition in n/a","id":"CVE-2019-18421","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"debian:debian_linux","products":["debian:debian_linux","fedoraproject:fedora","opensuse:leap","xen:xen"],"type":"race_condition","year":"2019"},"n_packages":0,"n_references":9,"next":{"headline":"Privilege escalation in n/a","id":"CVE-2019-18422"},"packages":[],"prev":{"headline":"Denial of service in n/a","id":"CVE-2019-18420"},"products":["n/a"],"published":"2019-10-31","related":[{"cvss_score":10,"headline":"ProFTPD Improper Access Control","id":"CVE-2015-3306","kev_date_added":"2026-10-08","published":"2015-05-18"},{"cvss_score":9.9,"headline":"RoundCube Webmail Deserialization of Untrusted Data","id":"CVE-2025-49113","kev_date_added":"2026-02-20","published":"2025-06-02"},{"cvss_score":9.8,"headline":"GNU InetUtils Argument Injection","id":"CVE-2026-24061","kev_date_added":"2026-01-26","published":"2026-01-21"},{"cvss_score":9.8,"headline":"Linux Kernel Improper Check for Unusual or Exceptional Conditions","id":"CVE-2025-39682","kev_date_added":"2026-09-18","published":"2025-09-05"},{"cvss_score":9.8,"headline":"Mozilla Firefox Use-After-Free","id":"CVE-2024-9680","kev_date_added":"2024-10-15","published":"2024-10-09"},{"cvss_score":9.8,"headline":"RARLAB UnRAR Directory Traversal","id":"CVE-2022-30333","kev_date_added":"2022-08-09","published":"2022-05-09"},{"cvss_score":9.8,"headline":"Roundcube Webmail SQL Injection","id":"CVE-2021-44026","kev_date_added":"2023-06-22","published":"2021-11-19"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2024-08-05","vendors":["n/a"]},"summary":"A malicious PV guest administrator can escalate privileges to the host OS by exploiting race conditions in Xen's pagetable promotion and demotion operations.","url":"https://insights.sbomify.com/CVE-2019-18421/"}