{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-47546","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-05-24T15:02:54.829Z","datePublished":"2024-05-24T15:09:51.286Z","dateUpdated":"2025-05-04T12:41:40.471Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2025-05-04T12:41:40.471Z"},"descriptions":[{"lang":"en","value":"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->flags` 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"}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/fib_rules.h","net/core/fib_rules.c","net/ipv4/fib_rules.c","net/ipv6/fib6_rules.c"],"versions":[{"version":"ca7a03c4175366a92cee0ccc4fec0038c3266e26","lessThan":"ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29","status":"affected","versionType":"git"},{"version":"ca7a03c4175366a92cee0ccc4fec0038c3266e26","lessThan":"209d35ee34e25f9668c404350a1c86d914c54ffa","status":"affected","versionType":"git"},{"version":"ca7a03c4175366a92cee0ccc4fec0038c3266e26","lessThan":"8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383","status":"affected","versionType":"git"},{"version":"ca7a03c4175366a92cee0ccc4fec0038c3266e26","lessThan":"cdef485217d30382f3bf6448c54b4401648fe3f1","status":"affected","versionType":"git"},{"version":"d37c966752043733eb847dd897d6e3405084c559","status":"affected","versionType":"git"},{"version":"ecc265624956ea784cb2bd2b31a95bd54c4f5f13","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/fib_rules.h","net/core/fib_rules.c","net/ipv4/fib_rules.c","net/ipv6/fib6_rules.c"],"versions":[{"version":"5.4","status":"affected"},{"version":"0","lessThan":"5.4","status":"unaffected","versionType":"semver"},{"version":"5.4.164","lessThanOrEqual":"5.4.*","status":"unaffected","versionType":"semver"},{"version":"5.10.84","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.7","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"5.16","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.4.164"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.10.84"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.15.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4","versionEndExcluding":"5.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.2.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3.4"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29"},{"url":"https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffa"},{"url":"https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383"},{"url":"https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1"}],"title":"ipv6: fix memory leak in fib6_rule_suppress","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2024-06-17T17:34:31.593424Z","id":"CVE-2021-47546","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2024-06-17T17:34:48.850Z"}},{"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2024-08-04T05:39:59.755Z"},"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffa","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1","tags":["x_transferred"]}]}]}}