{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-47118 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2021-47118 is a high-severity use after free vulnerability in Linux kernel, published on 15 Mar 2024. 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-2021-47118 and fix it if it is affected.\n\nWhat it is: CVE-2021-47118 is a high-severity use after free vulnerability in Linux kernel, published on 15 Mar 2024. 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-2021-47118 in the wild and no public exploit code.\n\nAffected product: Linux kernel. 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-2021-47118/ (Markdown: https://insights.sbomify.com/CVE-2021-47118/index.md)","id":"CVE-2021-47118","markdown":"https://insights.sbomify.com/CVE-2021-47118/index.md","name":"CVE-2021-47118","record":{"aliases":["DEBIAN-CVE-2021-47118","GHSA-f22j-p6f5-7h8x","UBUNTU-CVE-2021-47118"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["code_execution","privilege_escalation"],"network_reachable":"adjacent_or_local","non_default_config":false,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"A use-after-free vulnerability in the Linux kernel allows attackers to potentially execute arbitrary code or escalate privileges via signal delivery.","user_interaction":"not_required","vuln_class":"use_after_free"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"cvss":{"score":7.8,"severity":"high","source":"nvd","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"cwes":[{"id":"CWE-416","name":"Use After Free"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\npid: take a reference when initializing `cad_pid`\n\nDuring boot, kernel_init_freeable() initializes `cad_pid` to the init\ntask's struct pid.  Later on, we may change `cad_pid` via a sysctl, and\nwhen this happens proc_do_cad_pid() will increment the refcount on the\nnew pid via get_pid(), and will decrement the refcount on the old pid\nvia put_pid().  As we never called get_pid() when we initialized\n`cad_pid`, we decrement a reference we never incremented, can therefore\nfree the init task's struct pid early.  As there can be dangling\nreferences to the struct pid, we can later encounter a use-after-free\n(e.g.  when delivering signals).\n\nThis was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to\nhave been around since the conversion of `cad_pid` to struct pid in\ncommit 9ec52099e4b8 (\"[PATCH] replace cad_pid by a struct pid\") from the\npre-KASAN stone age of v2.6.19.\n\nFix this by getting a reference to the init task's struct pid when we\nassign it to `cad_pid`.\n\nFull KASAN splat below.\n\n   ==================================================================\n   BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]\n   BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n   Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273\n\n   CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1\n   Hardware name: linux,dummy-virt (DT)\n   Call trace:\n    ns_of_pid include/linux/pid.h:153 [inline]\n    task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n    do_notify_parent+0x308/0xe60 kernel/signal.c:1950\n    exit_notify kernel/exit.c:682 [inline]\n    do_exit+0x2334/0x2bd0 kernel/exit.c:845\n    do_group_exit+0x108/0x2c8 kernel/exit.c:922\n    get_signal+0x4e4/0x2a88 kernel/signal.c:2781\n    do_signal arch/arm64/kernel/signal.c:882 [inline]\n    do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936\n    work_pending+0xc/0x2dc\n\n   Allocated by task 0:\n    slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516\n    slab_alloc_node mm/slub.c:2907 [inline]\n    slab_alloc mm/slub.c:2915 [inline]\n    kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920\n    alloc_pid+0xdc/0xc00 kernel/pid.c:180\n    copy_process+0x2794/0x5e18 kernel/fork.c:2129\n    kernel_clone+0x194/0x13c8 kernel/fork.c:2500\n    kernel_thread+0xd4/0x110 kernel/fork.c:2552\n    rest_init+0x44/0x4a0 init/main.c:687\n    arch_call_rest_init+0x1c/0x28\n    start_kernel+0x520/0x554 init/main.c:1064\n    0x0\n\n   Freed by task 270:\n    slab_free_hook mm/slub.c:1562 [inline]\n    slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600\n    slab_free mm/slub.c:3161 [inline]\n    kmem_cache_free+0x224/0x8e0 mm/slub.c:3177\n    put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114\n    put_pid+0x30/0x48 kernel/pid.c:109\n    proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401\n    proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591\n    proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617\n    call_write_iter include/linux/fs.h:1977 [inline]\n    new_sync_write+0x3ac/0x510 fs/read_write.c:518\n    vfs_write fs/read_write.c:605 [inline]\n    vfs_write+0x9c4/0x1018 fs/read_write.c:585\n    ksys_write+0x124/0x240 fs/read_write.c:658\n    __do_sys_write fs/read_write.c:670 [inline]\n    __se_sys_write fs/read_write.c:667 [inline]\n    __arm64_sys_write+0x78/0xb0 fs/read_write.c:667\n    __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]\n    invoke_syscall arch/arm64/kernel/syscall.c:49 [inline]\n    el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129\n    do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168\n    el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416\n    el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432\n    el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701\n\n   The buggy address belongs to the object at ffff23794dda0000\n    which belongs to the cache pid of size 224\n   The buggy address is located 4 bytes inside of\n    224-byte region [ff\n---truncated---","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":"pid: take a reference when initializing `cad_pid`","id":"CVE-2021-47118","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"use_after_free","year":"2021"},"n_packages":0,"n_references":8,"next":{"headline":"ext4: fix memory leak in ext4_fill_super","id":"CVE-2021-47119"},"packages":[],"prev":{"headline":"ext4: fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed","id":"CVE-2021-47117"},"products":["Linux"],"published":"2024-03-15","related":[{"cvss_score":8.8,"headline":"Linux Kernel Out-of-Bounds Write","id":"CVE-2026-53266","kev_date_added":"2026-09-18","published":"2026-06-25"},{"cvss_score":8.8,"headline":"Linux Kernel Improper Input Validation","id":"CVE-2013-6282","kev_date_added":"2022-09-15","published":"2013-11-19"},{"cvss_score":8.4,"headline":"Linux Kernel Heap-Based Buffer Overflow","id":"CVE-2022-0185","kev_date_added":"2024-08-21","published":"2022-02-11"},{"cvss_score":8.4,"headline":"Linux Kernel Privilege Escalation","id":"CVE-2013-2094","kev_date_added":"2022-09-15","published":"2013-05-14"},{"cvss_score":7.8,"headline":"Linux Kernel Unspecified","id":"CVE-2026-53362","kev_date_added":"2026-08-27","published":"2026-07-04"},{"cvss_score":7.8,"headline":"Linux Kernel Missing Initialization of a Variable","id":"CVE-2026-46300","kev_date_added":"2026-10-28","published":"2026-05-23"},{"cvss_score":7.8,"headline":"Linux Kernel Race Condition","id":"CVE-2025-39964","kev_date_added":"2026-09-18","published":"2025-10-13"}],"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":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-05-11","vendors":["Linux"]},"summary":"A use-after-free vulnerability in the Linux kernel allows attackers to potentially execute arbitrary code or escalate privileges via signal delivery.","url":"https://insights.sbomify.com/CVE-2021-47118/"}