{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-4439 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2021-4439 is a high-severity memory corruption vulnerability in Linux kernel, published on 20 Jun 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-2021-4439 and fix it if it is affected.\n\nWhat it is: CVE-2021-4439 is a high-severity memory corruption vulnerability in Linux kernel, published on 20 Jun 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-2021-4439 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-2021-4439/ (Markdown: https://insights.sbomify.com/CVE-2021-4439/index.md)","id":"CVE-2021-4439","markdown":"https://insights.sbomify.com/CVE-2021-4439/index.md","name":"CVE-2021-4439","record":{"aliases":["DEBIAN-CVE-2021-4439","GHSA-gcrq-r544-wxfh","UBUNTU-CVE-2021-4439"],"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 local attacker can trigger an out-of-bounds array access in the Linux kernel ISDN CAPI driver, causing a system crash.","user_interaction":"not_required","vuln_class":"memory_corruption"},"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-129","name":"Improper Validation of Array Index"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nisdn: cpai: check ctr-\u003ecnr to avoid array index out of bound\n\nThe cmtp_add_connection() would add a cmtp session to a controller\nand run a kernel thread to process cmtp.\n\n\t__module_get(THIS_MODULE);\n\tsession-\u003etask = kthread_run(cmtp_session, session, \"kcmtpd_ctr_%d\",\n\t\t\t\t\t\t\t\tsession-\u003enum);\n\nDuring this process, the kernel thread would call detach_capi_ctr()\nto detach a register controller. if the controller\nwas not attached yet, detach_capi_ctr() would\ntrigger an array-index-out-bounds bug.\n\n[   46.866069][ T6479] UBSAN: array-index-out-of-bounds in\ndrivers/isdn/capi/kcapi.c:483:21\n[   46.867196][ T6479] index -1 is out of range for type 'capi_ctr *[32]'\n[   46.867982][ T6479] CPU: 1 PID: 6479 Comm: kcmtpd_ctr_0 Not tainted\n5.15.0-rc2+ #8\n[   46.869002][ T6479] Hardware name: QEMU Standard PC (i440FX + PIIX,\n1996), BIOS 1.14.0-2 04/01/2014\n[   46.870107][ T6479] Call Trace:\n[   46.870473][ T6479]  dump_stack_lvl+0x57/0x7d\n[   46.870974][ T6479]  ubsan_epilogue+0x5/0x40\n[   46.871458][ T6479]  __ubsan_handle_out_of_bounds.cold+0x43/0x48\n[   46.872135][ T6479]  detach_capi_ctr+0x64/0xc0\n[   46.872639][ T6479]  cmtp_session+0x5c8/0x5d0\n[   46.873131][ T6479]  ? __init_waitqueue_head+0x60/0x60\n[   46.873712][ T6479]  ? cmtp_add_msgpart+0x120/0x120\n[   46.874256][ T6479]  kthread+0x147/0x170\n[   46.874709][ T6479]  ? set_kthread_struct+0x40/0x40\n[   46.875248][ T6479]  ret_from_fork+0x1f/0x30\n[   46.875773][ T6479]","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":"isdn: cpai: check ctr-\u003ecnr to avoid array index out of bound","id":"CVE-2021-4439","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"memory_corruption","year":"2021"},"n_packages":0,"n_references":8,"next":{"headline":"x86/xen: Drop USERGS_SYSRET64 paravirt call","id":"CVE-2021-4440"},"packages":[],"prev":{"headline":"React Native Sms User Consent Intent Redirection Vulnerability","id":"CVE-2021-4438"},"products":["Linux"],"published":"2024-06-20","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 local attacker can trigger an out-of-bounds array access in the Linux kernel ISDN CAPI driver, causing a system crash.","url":"https://insights.sbomify.com/CVE-2021-4439/"}