CVE-2025-21864 (GCVE-0-2025-21864)
Vulnerability from cvelistv5
Published
2025-03-12 09:42
Modified
2025-10-01 19:26
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: tcp: drop secpath at the same time as we currently drop dst Xiumei reported hitting the WARN in xfrm6_tunnel_net_exit while running tests that boil down to: - create a pair of netns - run a basic TCP test over ipcomp6 - delete the pair of netns The xfrm_state found on spi_byaddr was not deleted at the time we delete the netns, because we still have a reference on it. This lingering reference comes from a secpath (which holds a ref on the xfrm_state), which is still attached to an skb. This skb is not leaked, it ends up on sk_receive_queue and then gets defer-free'd by skb_attempt_defer_free. The problem happens when we defer freeing an skb (push it on one CPU's defer_list), and don't flush that list before the netns is deleted. In that case, we still have a reference on the xfrm_state that we don't expect at this point. We already drop the skb's dst in the TCP receive path when it's no longer needed, so let's also drop the secpath. At this point, tcp_filter has already called into the LSM hooks that may require the secpath, so it should not be needed anymore. However, in some of those places, the MPTCP extension has just been attached to the skb, so we cannot simply drop all extensions.
References
Impacted products
Vendor Product Version
Linux Linux Version: 68822bdf76f10c3dc80609d4e2cdc1e847429086
Version: 68822bdf76f10c3dc80609d4e2cdc1e847429086
Version: 68822bdf76f10c3dc80609d4e2cdc1e847429086
Version: 68822bdf76f10c3dc80609d4e2cdc1e847429086
Version: 68822bdf76f10c3dc80609d4e2cdc1e847429086
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    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 5.5, \"attackVector\": \"LOCAL\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"LOW\", \"confidentialityImpact\": \"NONE\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2025-21864\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2025-10-01T19:25:34.148914Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-476\", \"description\": \"CWE-476 NULL Pointer Dereference\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2025-10-01T16:58:42.237Z\"}}], \"cna\": {\"title\": \"tcp: drop secpath at the same time as we currently drop dst\", \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"68822bdf76f10c3dc80609d4e2cdc1e847429086\", \"lessThan\": \"87858bbf21da239ace300d61dd209907995c0491\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"68822bdf76f10c3dc80609d4e2cdc1e847429086\", \"lessThan\": \"f1d5e6a5e468308af7759cf5276779d3155c5e98\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"68822bdf76f10c3dc80609d4e2cdc1e847429086\", \"lessThan\": \"cd34a07f744451e2ecf9005bb7d24d0b2fb83656\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"68822bdf76f10c3dc80609d4e2cdc1e847429086\", \"lessThan\": \"69cafd9413084cd5012cf5d7c7ec6f3d493726d9\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"68822bdf76f10c3dc80609d4e2cdc1e847429086\", \"lessThan\": \"9b6412e6979f6f9e0632075f8f008937b5cd4efd\", \"versionType\": \"git\"}], \"programFiles\": [\"include/net/tcp.h\", \"net/ipv4/tcp_fastopen.c\", \"net/ipv4/tcp_input.c\", \"net/ipv4/tcp_ipv4.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.19\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.19\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"6.1.130\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.80\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.17\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.13.5\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.13.*\"}, {\"status\": \"unaffected\", \"version\": \"6.14\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"include/net/tcp.h\", \"net/ipv4/tcp_fastopen.c\", \"net/ipv4/tcp_input.c\", \"net/ipv4/tcp_ipv4.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/87858bbf21da239ace300d61dd209907995c0491\"}, {\"url\": \"https://git.kernel.org/stable/c/f1d5e6a5e468308af7759cf5276779d3155c5e98\"}, {\"url\": \"https://git.kernel.org/stable/c/cd34a07f744451e2ecf9005bb7d24d0b2fb83656\"}, {\"url\": \"https://git.kernel.org/stable/c/69cafd9413084cd5012cf5d7c7ec6f3d493726d9\"}, {\"url\": \"https://git.kernel.org/stable/c/9b6412e6979f6f9e0632075f8f008937b5cd4efd\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\ntcp: drop secpath at the same time as we currently drop dst\\n\\nXiumei reported hitting the WARN in xfrm6_tunnel_net_exit while\\nrunning tests that boil down to:\\n - create a pair of netns\\n - run a basic TCP test over ipcomp6\\n - delete the pair of netns\\n\\nThe xfrm_state found on spi_byaddr was not deleted at the time we\\ndelete the netns, because we still have a reference on it. This\\nlingering reference comes from a secpath (which holds a ref on the\\nxfrm_state), which is still attached to an skb. This skb is not\\nleaked, it ends up on sk_receive_queue and then gets defer-free\u0027d by\\nskb_attempt_defer_free.\\n\\nThe problem happens when we defer freeing an skb (push it on one CPU\u0027s\\ndefer_list), and don\u0027t flush that list before the netns is deleted. In\\nthat case, we still have a reference on the xfrm_state that we don\u0027t\\nexpect at this point.\\n\\nWe already drop the skb\u0027s dst in the TCP receive path when it\u0027s no\\nlonger needed, so let\u0027s also drop the secpath. At this point,\\ntcp_filter has already called into the LSM hooks that may require the\\nsecpath, so it should not be needed anymore. However, in some of those\\nplaces, the MPTCP extension has just been attached to the skb, so we\\ncannot simply drop all extensions.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.130\", \"versionStartIncluding\": \"5.19\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.80\", \"versionStartIncluding\": \"5.19\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.17\", \"versionStartIncluding\": \"5.19\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.13.5\", \"versionStartIncluding\": \"5.19\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.14\", \"versionStartIncluding\": \"5.19\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2025-05-04T07:22:47.376Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2025-21864\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-10-01T19:26:37.158Z\", \"dateReserved\": \"2024-12-29T08:45:45.780Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2025-03-12T09:42:21.223Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}


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