{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-63951 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-63951 is a high-severity use after free vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-63951 and fix it if it is affected.\n\nWhat it is: CVE-2026-63951 is a high-severity use after free vulnerability in Linux, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-63951 in the wild and no public exploit code.\n\nAffected product: 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-2026-63951/ (Markdown: https://insights.sbomify.com/CVE-2026-63951/index.md)","id":"CVE-2026-63951","markdown":"https://insights.sbomify.com/CVE-2026-63951/index.md","name":"CVE-2026-63951","record":{"aliases":["DEBIAN-CVE-2026-63951","GHSA-jmwm-428x-w863","UBUNTU-CVE-2026-63951"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"A race condition in the Linux kernel zram writeback handler causes a use-after-free, leading to a system crash.","user_interaction":"not_required","vuln_class":"use_after_free"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[],"cvss":{"score":7.8,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nzram: fix use-after-free in zram_writeback_endio\n\nA crash was observed in zram_writeback_endio due to a NULL pointer\ndereference in wake_up.  The root cause is a race condition between the\nbio completion handler (zram_writeback_endio) and the writeback task.\n\nIn zram_writeback_endio, wake_up() is called on \u0026wb_ctl-\u003edone_wait after\nreleasing wb_ctl-\u003edone_lock.  This creates a race window where the\nwriteback task can see num_inflight become 0, return, and free wb_ctl\nbefore zram_writeback_endio calls wake_up().\n\nCPU 0 (zram_writeback_endio)     CPU 1 (writeback_store)\n============================     ============================\n                                 zram_writeback_slots\n                                   zram_submit_wb_request\n                                   zram_submit_wb_request\n                                   wait_event(wb_ctl-\u003edone_wait)\nspin_lock(\u0026wb_ctl-\u003edone_lock);\nlist_add(\u0026req-\u003eentry, \u0026wb_ctl-\u003edone_reqs);\nspin_unlock(\u0026wb_ctl-\u003edone_lock);\nwake_up(\u0026wb_ctl-\u003edone_wait);\n                                   zram_complete_done_reqs\nspin_lock(\u0026wb_ctl-\u003edone_lock);\nlist_add(\u0026req-\u003eentry, \u0026wb_ctl-\u003edone_reqs);\nspin_unlock(\u0026wb_ctl-\u003edone_lock);\n                                   while (num_inflight) \u003e 0)\n                                     spin_lock(\u0026wb_ctl-\u003edone_lock);\n                                     list_del(\u0026req-\u003eentry);\n                                     spin_unlock(\u0026wb_ctl-\u003edone_lock);\n                                     // num_inflight becomes 0\n                                     atomic_dec(num_inflight);\n\n                                 // Leave zram_writeback_slots\n                                 // Free wb_ctl\n                                 release_wb_ctl(wb_ctl);\n// UAF crash!\nwake_up(\u0026wb_ctl-\u003edone_wait);\n\nThis patch fixes this race by using RCU.  By protecting wb_ctl with\nrcu_read_lock() in zram_writeback_endio and using kfree_rcu() to free it,\nwe ensure that wb_ctl remains valid during the execution of\nzram_writeback_endio.","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":"zram: fix use-after-free in zram_writeback_endio","id":"CVE-2026-63951","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"use_after_free","year":"2026"},"n_packages":0,"n_references":2,"next":{"headline":"memfd: deny writeable mappings when implying SEAL_WRITE","id":"CVE-2026-63952"},"packages":[],"prev":{"headline":"mm/rmap: initialize nr_pages to 1 at loop start in try_to_unmap_one","id":"CVE-2026-63950"},"products":["Linux"],"published":"2026-07-19","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-08-05","vendors":["Linux"]},"summary":"A race condition in the Linux kernel zram writeback handler causes a use-after-free, leading to a system crash.","url":"https://insights.sbomify.com/CVE-2026-63951/"}