{"cve":"CVE-2024-57974","nvd":{"published":"2025-02-27T02:15:10.590","modified":"2026-10-21T13:17:53.193","status":"Modified","description":"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(), 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---","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","score":4.7},"cwes":["CWE-362"],"references":["https://git.kernel.org/stable/c/2855445a1870b8e568fb19edbd60b9c499e3dae0","https://git.kernel.org/stable/c/4f8344fce91c5766d368edb0ad80142eacd805c7","https://git.kernel.org/stable/c/a502ea6fa94b1f7be72a24bcf9e3f5f6b7e6e90c","https://git.kernel.org/stable/c/d65d3bf309b2649d27b24efd0d8784da2d81f2a6"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-22T16:41:11.231219466+00:00"},"epss":{"cve":"CVE-2024-57974","score":0.00181,"percentile":0.07641,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}