{"id":"CVE-2021-47010","state":"PUBLISHED","title":"net: Only allow init netns to set default tcp cong to a restricted algo","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: Only allow init netns to set default tcp cong to a restricted algo\n\ntcp_set_default_congestion_control() is netns-safe in that it writes\nto &net->ipv4.tcp_congestion_control, but it also sets\nca->flags |= TCP_CONG_NON_RESTRICTED which is not namespaced.\nThis has the unintended side-effect of changing the global\nnet.ipv4.tcp_allowed_congestion_control sysctl, despite the fact that it\nis read-only: 97684f0970f6 (\"net: Make tcp_allowed_congestion_control\nreadonly in non-init netns\")\n\nResolve this netns \"leak\" by only allowing the init netns to set the\ndefault algorithm to one that is restricted. This restriction could be\nremoved if tcp_allowed_congestion_control were namespace-ified in the\nfuture.\n\nThis bug was uncovered with\nhttps://github.com/JonathonReinhart/linux-netns-sysctl-verify","publishedAt":"2024-02-28T08:13:29.051Z","updatedAt":"2026-05-11T13:46:12.794Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"CISA-ADP"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"992de06308d9a9584d59b96d294ac676f924e437","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"9884f745108f7d25b189bbcd6754e284fb29ab68","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"6c1ea8bee75df8fe2184a50fcd0f70bf82986f42","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"efe1532a6e1a8e3c343d04fff510f0ed80328f9c","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"e7d7bedd507bb732e600403b7a96f9fe48d0ca31","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"8d432592f30fcc34ef5a10aac4887b4897884493","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/tcp_cong.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"semver"},{"version":"4.19.191","status":"unaffected","lessThanOrEqual":"4.19.*","versionType":"semver"},{"version":"5.4.119","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.37","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.11.21","status":"unaffected","lessThanOrEqual":"5.11.*","versionType":"semver"},{"version":"5.12.4","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/tcp_cong.c"]}],"references":["https://git.kernel.org/stable/c/992de06308d9a9584d59b96d294ac676f924e437","https://git.kernel.org/stable/c/9884f745108f7d25b189bbcd6754e284fb29ab68","https://git.kernel.org/stable/c/6c1ea8bee75df8fe2184a50fcd0f70bf82986f42","https://git.kernel.org/stable/c/efe1532a6e1a8e3c343d04fff510f0ed80328f9c","https://git.kernel.org/stable/c/e7d7bedd507bb732e600403b7a96f9fe48d0ca31","https://git.kernel.org/stable/c/8d432592f30fcc34ef5a10aac4887b4897884493"],"weaknesses":["CWE-400"],"ingestedAt":"2026-10-29T19:49:19.404Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/47xxx/CVE-2021-47010.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47010","state":"PUBLISHED","datePublished":"2024-02-28T08:13:29.051Z","dateUpdated":"2026-05-11T13:46:12.794Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-02-27T18:42:55.953Z"},"containers":{"cna":{"title":"net: Only allow init netns to set default tcp cong to a restricted algo","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: Only allow init netns to set default tcp cong to a restricted algo\n\ntcp_set_default_congestion_control() is netns-safe in that it writes\nto &net->ipv4.tcp_congestion_control, but it also sets\nca->flags |= TCP_CONG_NON_RESTRICTED which is not namespaced.\nThis has the unintended side-effect of changing the global\nnet.ipv4.tcp_allowed_congestion_control sysctl, despite the fact that it\nis read-only: 97684f0970f6 (\"net: Make tcp_allowed_congestion_control\nreadonly in non-init netns\")\n\nResolve this netns \"leak\" by only allowing the init netns to set the\ndefault algorithm to one that is restricted. This restriction could be\nremoved if tcp_allowed_congestion_control were namespace-ified in the\nfuture.\n\nThis bug was uncovered with\nhttps://github.com/JonathonReinhart/linux-netns-sysctl-verify"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"992de06308d9a9584d59b96d294ac676f924e437","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"9884f745108f7d25b189bbcd6754e284fb29ab68","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"6c1ea8bee75df8fe2184a50fcd0f70bf82986f42","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"efe1532a6e1a8e3c343d04fff510f0ed80328f9c","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"e7d7bedd507bb732e600403b7a96f9fe48d0ca31","versionType":"git"},{"version":"6670e152447732ba90626f36dfc015a13fbf150e","status":"affected","lessThan":"8d432592f30fcc34ef5a10aac4887b4897884493","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/tcp_cong.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"semver"},{"version":"4.19.191","status":"unaffected","lessThanOrEqual":"4.19.*","versionType":"semver"},{"version":"5.4.119","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.37","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.11.21","status":"unaffected","lessThanOrEqual":"5.11.*","versionType":"semver"},{"version":"5.12.4","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/tcp_cong.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/992de06308d9a9584d59b96d294ac676f924e437"},{"url":"https://git.kernel.org/stable/c/9884f745108f7d25b189bbcd6754e284fb29ab68"},{"url":"https://git.kernel.org/stable/c/6c1ea8bee75df8fe2184a50fcd0f70bf82986f42"},{"url":"https://git.kernel.org/stable/c/efe1532a6e1a8e3c343d04fff510f0ed80328f9c"},{"url":"https://git.kernel.org/stable/c/e7d7bedd507bb732e600403b7a96f9fe48d0ca31"},{"url":"https://git.kernel.org/stable/c/8d432592f30fcc34ef5a10aac4887b4897884493"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T13:46:12.794Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"4.19.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.4.119"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.10.37"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.11.21"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.12.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.15","versionEndExcluding":"5.13"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/992de06308d9a9584d59b96d294ac676f924e437","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/9884f745108f7d25b189bbcd6754e284fb29ab68","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/6c1ea8bee75df8fe2184a50fcd0f70bf82986f42","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/efe1532a6e1a8e3c343d04fff510f0ed80328f9c","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/e7d7bedd507bb732e600403b7a96f9fe48d0ca31","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/8d432592f30fcc34ef5a10aac4887b4897884493","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-04T05:24:39.534Z"}},{"title":"CISA ADP Vulnrichment","affected":[{"vendor":"linux","product":"linux_kernel","defaultStatus":"unknown","versions":[{"version":"6670e1524477","status":"affected","lessThan":"992de06308d9","versionType":"custom"},{"version":"6670e1524477","status":"affected","lessThan":"9884f745108f","versionType":"custom"},{"version":"6670e1524477","status":"affected","lessThan":"6c1ea8bee75d","versionType":"custom"},{"version":"6670e1524477","status":"affected","lessThan":"efe1532a6e1a","versionType":"custom"},{"version":"6670e1524477","status":"affected","lessThan":"e7d7bedd507b","versionType":"custom"},{"version":"6670e1524477","status":"affected","lessThan":"8d432592f30f","versionType":"custom"},{"version":"4.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.15","versionType":"custom"},{"version":"4.19.191","status":"unaffected","lessThanOrEqual":"4.20","versionType":"custom"},{"version":"5.4.119","status":"unaffected","lessThanOrEqual":"5.5","versionType":"custom"},{"version":"5.10.37","status":"unaffected","lessThanOrEqual":"5.11","versionType":"custom"},{"version":"5.11.21","status":"unaffected","lessThanOrEqual":"5.12","versionType":"custom"},{"version":"5.12.4","status":"unaffected","lessThanOrEqual":"5.13","versionType":"custom"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"custom"}],"cpes":["cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*"]}],"metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.8,"attackVector":"LOCAL","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"timestamp":"2024-07-25T15:24:31.511356Z","id":"CVE-2021-47010","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","type":"CWE","lang":"en","description":"CWE-400 Uncontrolled Resource Consumption"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-08-07T15:25:44.662Z"}}]}}}