{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2025-21921 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2025-21921 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 2025. 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-2025-21921 and fix it if it is affected.\n\nWhat it is: CVE-2025-21921 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 2025. 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-2025-21921 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-2025-21921/ (Markdown: https://insights.sbomify.com/CVE-2025-21921/index.md)","id":"CVE-2025-21921","markdown":"https://insights.sbomify.com/CVE-2025-21921/index.md","name":"CVE-2025-21921","record":{"aliases":["BELL-CVE-2025-21921","DEBIAN-CVE-2025-21921","GHSA-qc6x-3767-556f","UBUNTU-CVE-2025-21921"],"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 null pointer dereference in the Linux kernel ethtool netlink subsystem allows local attackers to cause a system crash via specific PLCA commands.","user_interaction":"not_required","vuln_class":"null_dereference"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"Linux","cpe":[{"product":"linux_kernel","vendor":"linux"}],"cvss":{"score":5.5,"severity":"medium","source":"nvd","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[{"id":"CWE-476","name":"NULL Pointer Dereference"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ethtool: netlink: Allow NULL nlattrs when getting a phy_device\n\nethnl_req_get_phydev() is used to lookup a phy_device, in the case an\nethtool netlink command targets a specific phydev within a netdev's\ntopology.\n\nIt takes as a parameter a const struct nlattr *header that's used for\nerror handling :\n\n       if (!phydev) {\n               NL_SET_ERR_MSG_ATTR(extack, header,\n                                   \"no phy matching phyindex\");\n               return ERR_PTR(-ENODEV);\n       }\n\nIn the notify path after a -\u003eset operation however, there's no request\nattributes available.\n\nThe typical callsite for the above function looks like:\n\n\tphydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_XXX_HEADER],\n\t\t\t\t      info-\u003eextack);\n\nSo, when tb is NULL (such as in the ethnl notify path), we have a nice\ncrash.\n\nIt turns out that there's only the PLCA command that is in that case, as\nthe other phydev-specific commands don't have a notification.\n\nThis commit fixes the crash by passing the cmd index and the nlattr\narray separately, allowing NULL-checking it directly inside the helper.","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":"net: ethtool: netlink: Allow NULL nlattrs when getting a phy_device","id":"CVE-2025-21921","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"null_dereference","year":"2025"},"n_packages":0,"n_references":3,"next":{"headline":"ppp: Fix KMSAN uninit-value warning with bpf","id":"CVE-2025-21922"},"packages":[],"prev":{"headline":"vlan: enforce underlying device type","id":"CVE-2025-21920"},"products":["Linux"],"published":"2025-04-01","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":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-05-11","vendors":["Linux"]},"summary":"A null pointer dereference in the Linux kernel ethtool netlink subsystem allows local attackers to cause a system crash via specific PLCA commands.","url":"https://insights.sbomify.com/CVE-2025-21921/"}