{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2021-47546 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2021-47546 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 May 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-2021-47546 and fix it if it is affected.\n\nWhat it is: CVE-2021-47546 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 May 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-2021-47546 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-2021-47546/ (Markdown: https://insights.sbomify.com/CVE-2021-47546/index.md)","id":"CVE-2021-47546","markdown":"https://insights.sbomify.com/CVE-2021-47546/index.md","name":"CVE-2021-47546","record":{"aliases":["DEBIAN-CVE-2021-47546","UBUNTU-CVE-2021-47546"],"analysis":{"component_type":"kernel","fix_type":"patch","impacts":["denial_of_service"],"network_reachable":"adjacent_or_local","non_default_config":true,"product_category":"Linux kernel","requires_auth":"low_privilege","summary":"A memory leak in the Linux kernel IPv6 routing code allows remote attackers to cause a denial of service via crafted network traffic.","user_interaction":"not_required","vuln_class":"denial_of_service"},"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-401","name":"Missing Release of Memory after Effective Lifetime"}],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: fix memory leak in fib6_rule_suppress\n\nThe kernel leaks memory when a `fib` rule is present in IPv6 nftables\nfirewall rules and a suppress_prefix rule is present in the IPv6 routing\nrules (used by certain tools such as wg-quick). In such scenarios, every\nincoming packet will leak an allocation in `ip6_dst_cache` slab cache.\n\nAfter some hours of `bpftrace`-ing and source code reading, I tracked\ndown the issue to ca7a03c41753 (\"ipv6: do not free rt if\nFIB_LOOKUP_NOREF is set on suppress rule\").\n\nThe problem with that change is that the generic `args-\u003eflags` always have\n`FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag\n`RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not\ndecreasing the refcount when needed.\n\nHow to reproduce:\n - Add the following nftables rule to a prerouting chain:\n     meta nfproto ipv6 fib saddr . mark . iif oif missing drop\n   This can be done with:\n     sudo nft create table inet test\n     sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }'\n     sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop\n - Run:\n     sudo ip -6 rule add table main suppress_prefixlength 0\n - Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase\n   with every incoming ipv6 packet.\n\nThis patch exposes the protocol-specific flags to the protocol\nspecific `suppress` function, and check the protocol-specific `flags`\nargument for RT6_LOOKUP_F_DST_NOREF instead of the generic\nFIB_LOOKUP_NOREF when decreasing the refcount, like this.\n\n[1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71\n[2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99","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":"ipv6: fix memory leak in fib6_rule_suppress","id":"CVE-2021-47546","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":"linux:linux_kernel","products":["linux:linux_kernel"],"type":"denial_of_service","year":"2021"},"n_packages":0,"n_references":4,"next":{"headline":"net: tulip: de4x5: fix the problem that the array 'lp-\u003ephy[8]' may be out of bound","id":"CVE-2021-47547"},"packages":[],"prev":{"headline":"This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.","id":"CVE-2021-47545"},"products":["Linux"],"published":"2024-05-24","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":"2026-05-23","vendors":["Linux"]},"summary":"A memory leak in the Linux kernel IPv6 routing code allows remote attackers to cause a denial of service via crafted network traffic.","url":"https://insights.sbomify.com/CVE-2021-47546/"}