{"id":"CVE-2024-57974","title":"udp: Deal with race between UDP socket address change and rehash","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nudp: Deal with race between UDP socket address change and rehash\n\nIf a UDP socket changes its local address while it's receiving\ndatagrams, as a result of connect(), th…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < 3946283de7bbb76b2995bd51ab0388d4fd556c77","Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < 2855445a1870b8e568fb19edbd60b9c499e3dae0","Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < 4f8344fce91c5766d368edb0ad80142eacd805c7","Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < d65d3bf309b2649d27b24efd0d8784da2d81f2a6","Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < a502ea6fa94b1f7be72a24bcf9e3f5f6b7e6e90c","Linux 2.6.33"],"published":"2025-02-27","updated":"2026-10-30","sourceUpdated":"2026-10-30T12:20:32.080Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2024-57974","references":[{"url":"https://git.kernel.org/stable/c/3946283de7bbb76b2995bd51ab0388d4fd556c77"},{"url":"https://git.kernel.org/stable/c/2855445a1870b8e568fb19edbd60b9c499e3dae0"},{"url":"https://git.kernel.org/stable/c/4f8344fce91c5766d368edb0ad80142eacd805c7"},{"url":"https://git.kernel.org/stable/c/d65d3bf309b2649d27b24efd0d8784da2d81f2a6"},{"url":"https://git.kernel.org/stable/c/a502ea6fa94b1f7be72a24bcf9e3f5f6b7e6e90c"}],"tags":["cve.org"],"epss":0.00181,"epssPercentile":0.077,"ingestedAt":"2026-10-21T12:48:53.722Z","slug":"CVE-2024-57974","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nudp: Deal with race between UDP socket address change and rehash\n\nIf a UDP socket changes its local address while it's receiving\ndatagrams, as a result of connect(), there is a period during which\na lookup operation might fail to find it, after the address is changed\nbut before the secondary hash (port and address) and the four-tuple\nhash (local and remote ports and addresses) are updated.\n\nSecondary hash chains were introduced by commit 30fff9231fad (\"udp:\nbind() optimisation\") and, as a result, a rehash operation became\nneeded to make a bound socket reachable again after a connect().\n\nThis operation was introduced by commit 719f835853a9 (\"udp: add\nrehash on connect()\") which isn't however a complete fix: the\nsocket will be found once the rehashing completes, but not while\nit's pending.\n\nThis is noticeable with a socat(1) server in UDP4-LISTEN mode, and a\nclient sending datagrams to it. After the server receives the first\ndatagram (cf. _xioopen_ipdgram_listen()), it issues a connect() to\nthe address of the sender, in order to set up a directed flow.\n\nNow, if the client, running on a different CPU thread, happens to\nsend a (subsequent) datagram while the server's socket changes its\naddress, but is not rehashed yet, this will result in a failed\nlookup and a port unreachable error delivered to the client, as\napparent from the following reproducer:\n\n  LEN=$(($(cat /proc/sys/net/core/wmem_default) / 4))\n  dd if=/dev/urandom bs=1 count=${LEN} of=tmp.in\n\n  while :; do\n  \ttaskset -c 1 socat UDP4-LISTEN:1337,null-eof OPEN:tmp.out,create,trunc &\n  \tsleep 0.1 || sleep 1\n  \ttaskset -c 2 socat OPEN:tmp.in UDP4:localhost:1337,shut-null\n  \twait\n  done\n\nwhere the client will eventually get ECONNREFUSED on a write()\n(typically the second or third one of a given iteration):\n\n  2024/11/13 21:28:23 socat[46901] E write(6, 0x556db2e3c000, 8192): Connection refused\n\nThis issue was first observed as a seldom failure in Podman's tests\nchecking UDP functionality while using pasta(1) to connect the\ncontainer's network namespace, which leads us to a reproducer with\nthe lookup error resulting in an ICMP packet on a tap device:\n\n  LOCAL_ADDR=\"$(ip -j -4 addr show|jq -rM '.[] | .addr_info[0] | select(.scope == \"global\").local')\"\n\n  while :; do\n  \t./pasta --config-net -p pasta.pcap -u 1337 socat UDP4-LISTEN:1337,null-eof OPEN:tmp.out,create,trunc &\n  \tsleep 0.2 || sleep 1\n  \tsocat OPEN:tmp.in UDP4:${LOCAL_ADDR}:1337,shut-null\n  \twait\n  \tcmp tmp.in tmp.out\n  done\n\nOnce this fails:\n\n  tmp.in tmp.out differ: char 8193, line 29\n\nwe can finally have a look at what's going on:\n\n  $ tshark -r pasta.pcap\n      1   0.000000           :: ? ff02::16     ICMPv6 110 Multicast Listener Report Message v2\n      2   0.168690 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192\n      3   0.168767 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192\n      4   0.168806 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192\n      5   0.168827 c6:47:05:8d:dc:04 ? Broadcast    ARP 42 Who has 88.198.0.161? Tell 88.198.0.164\n      6   0.168851 9a:55:9a:55:9a:55 ? c6:47:05:8d:dc:04 ARP 42 88.198.0.161 is at 9a:55:9a:55:9a:55\n      7   0.168875 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192\n      8   0.168896 88.198.0.164 ? 88.198.0.161 ICMP 590 Destination unreachable (Port unreachable)\n      9   0.168926 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192\n     10   0.168959 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192\n     11   0.168989 88.198.0.161 ? 88.198.0.164 UDP 4138 60260 ? 1337 Len=4096\n     12   0.169010 88.198.0.161 ? 88.198.0.164 UDP 42 60260 ? 1337 Len=0\n\nOn the third datagram received, the network namespace of the container\ninitiates an ARP lookup to deliver the ICMP message.\n\nIn another variant of this reproducer, starting the client with:\n\n  strace -f pasta --config-net -u 1337 socat UDP4-LISTEN:1337,null-eof OPEN:tmp.out,create,tru\n---truncated---\n\n## Affected\n\n- `Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < 3946283de7bbb76b2995bd51ab0388d4fd556c77`\n- `Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < 2855445a1870b8e568fb19edbd60b9c499e3dae0`\n- `Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < 4f8344fce91c5766d368edb0ad80142eacd805c7`\n- `Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < d65d3bf309b2649d27b24efd0d8784da2d81f2a6`\n- `Linux >= 30fff9231fad757c061285e347b33c5149c2c2e4 < a502ea6fa94b1f7be72a24bcf9e3f5f6b7e6e90c`\n- `Linux 2.6.33`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}