{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-46921 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2021-46921 is a high-severity vulnerability in Linux kernel, published on 27 Feb 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-2021-46921 and fix it if it is affected.\n\nWhat it is: CVE-2021-46921 is a high-severity vulnerability in Linux kernel, published on 27 Feb 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-2021-46921 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-2021-46921/ (Markdown: https://insights.sbomify.com/CVE-2021-46921/index.md)","id":"CVE-2021-46921","markdown":"https://insights.sbomify.com/CVE-2021-46921/index.md","name":"CVE-2021-46921","record":{"aliases":["DEBIAN-CVE-2021-46921","GHSA-8j25-5vwv-hm2f","UBUNTU-CVE-2021-46921"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["data_read","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's qrwlock implementation allows readers to observe stale data, potentially causing system instability or information disclosure.","user_interaction":"not_required","vuln_class":"race_condition"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"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":[{"id":"CWE-668","name":"Exposure of Resource to Wrong Sphere"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nlocking/qrwlock: Fix ordering in queued_write_lock_slowpath()\n\nWhile this code is executed with the wait_lock held, a reader can\nacquire the lock without holding wait_lock.  The writer side loops\nchecking the value with the atomic_cond_read_acquire(), but only truly\nacquires the lock when the compare-and-exchange is completed\nsuccessfully which isn’t ordered. This exposes the window between the\nacquire and the cmpxchg to an A-B-A problem which allows reads\nfollowing the lock acquisition to observe values speculatively before\nthe write lock is truly acquired.\n\nWe've seen a problem in epoll where the reader does a xchg while\nholding the read lock, but the writer can see a value change out from\nunder it.\n\n  Writer                                | Reader\n  --------------------------------------------------------------------------------\n  ep_scan_ready_list()                  |\n  |- write_lock_irq()                   |\n      |- queued_write_lock_slowpath()   |\n\t|- atomic_cond_read_acquire()   |\n\t\t\t\t        | read_lock_irqsave(\u0026ep-\u003elock, flags);\n     --\u003e (observes value before unlock) |  chain_epi_lockless()\n     |                                  |    epi-\u003enext = xchg(\u0026ep-\u003eovflist, epi);\n     |                                  | read_unlock_irqrestore(\u0026ep-\u003elock, flags);\n     |                                  |\n     |     atomic_cmpxchg_relaxed()     |\n     |-- READ_ONCE(ep-\u003eovflist);        |\n\nA core can order the read of the ovflist ahead of the\natomic_cmpxchg_relaxed(). Switching the cmpxchg to use acquire\nsemantics addresses this issue at which point the atomic_cond_read can\nbe switched to use relaxed semantics.\n\n[peterz: use try_cmpxchg()]","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":"locking/qrwlock: Fix ordering in queued_write_lock_slowpath()","id":"CVE-2021-46921","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"race_condition","year":"2021"},"n_packages":0,"n_references":5,"next":{"headline":"KEYS: trusted: Fix TPM reservation for seal/unseal","id":"CVE-2021-46922"},"packages":[],"prev":{"headline":"dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback","id":"CVE-2021-46920"},"products":["Linux"],"published":"2024-02-27","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":"2026-08-05","vendors":["Linux"]},"summary":"A race condition in the Linux kernel's qrwlock implementation allows readers to observe stale data, potentially causing system instability or information disclosure.","url":"https://insights.sbomify.com/CVE-2021-46921/"}