CVE-2026-31503 (GCVE-0-2026-31503)
Vulnerability from cvelistv5
Published
2026-04-22 13:54
Modified
2026-04-22 13:54
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
udp: Fix wildcard bind conflict check when using hash2
When binding a udp_sock to a local address and port, UDP uses
two hashes (udptable->hash and udptable->hash2) for collision
detection. The current code switches to "hash2" when
hslot->count > 10.
"hash2" is keyed by local address and local port.
"hash" is keyed by local port only.
The issue can be shown in the following bind sequence (pseudo code):
bind(fd1, "[fd00::1]:8888")
bind(fd2, "[fd00::2]:8888")
bind(fd3, "[fd00::3]:8888")
bind(fd4, "[fd00::4]:8888")
bind(fd5, "[fd00::5]:8888")
bind(fd6, "[fd00::6]:8888")
bind(fd7, "[fd00::7]:8888")
bind(fd8, "[fd00::8]:8888")
bind(fd9, "[fd00::9]:8888")
bind(fd10, "[fd00::10]:8888")
/* Correctly return -EADDRINUSE because "hash" is used
* instead of "hash2". udp_lib_lport_inuse() detects the
* conflict.
*/
bind(fail_fd, "[::]:8888")
/* After one more socket is bound to "[fd00::11]:8888",
* hslot->count exceeds 10 and "hash2" is used instead.
*/
bind(fd11, "[fd00::11]:8888")
bind(fail_fd, "[::]:8888") /* succeeds unexpectedly */
The same issue applies to the IPv4 wildcard address "0.0.0.0"
and the IPv4-mapped wildcard address "::ffff:0.0.0.0". For
example, if there are existing sockets bound to
"192.168.1.[1-11]:8888", then binding "0.0.0.0:8888" or
"[::ffff:0.0.0.0]:8888" can also miss the conflict when
hslot->count > 10.
TCP inet_csk_get_port() already has the correct check in
inet_use_bhash2_on_bind(). Rename it to
inet_use_hash2_on_bind() and move it to inet_hashtables.h
so udp.c can reuse it in this fix.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 30fff9231fad757c061285e347b33c5149c2c2e4 Version: 30fff9231fad757c061285e347b33c5149c2c2e4 Version: 30fff9231fad757c061285e347b33c5149c2c2e4 Version: 30fff9231fad757c061285e347b33c5149c2c2e4 Version: 30fff9231fad757c061285e347b33c5149c2c2e4 Version: 30fff9231fad757c061285e347b33c5149c2c2e4 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"include/net/inet_hashtables.h",
"net/ipv4/inet_connection_sock.c",
"net/ipv4/udp.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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{
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]
},
{
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"programFiles": [
"include/net/inet_hashtables.h",
"net/ipv4/inet_connection_sock.c",
"net/ipv4/udp.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"version": "2.6.33"
},
{
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.168",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.131",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.80",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.21",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.11",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.168",
"versionStartIncluding": "2.6.33",
"vulnerable": true
},
{
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{
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{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nudp: Fix wildcard bind conflict check when using hash2\n\nWhen binding a udp_sock to a local address and port, UDP uses\ntwo hashes (udptable-\u003ehash and udptable-\u003ehash2) for collision\ndetection. The current code switches to \"hash2\" when\nhslot-\u003ecount \u003e 10.\n\n\"hash2\" is keyed by local address and local port.\n\"hash\" is keyed by local port only.\n\nThe issue can be shown in the following bind sequence (pseudo code):\n\nbind(fd1, \"[fd00::1]:8888\")\nbind(fd2, \"[fd00::2]:8888\")\nbind(fd3, \"[fd00::3]:8888\")\nbind(fd4, \"[fd00::4]:8888\")\nbind(fd5, \"[fd00::5]:8888\")\nbind(fd6, \"[fd00::6]:8888\")\nbind(fd7, \"[fd00::7]:8888\")\nbind(fd8, \"[fd00::8]:8888\")\nbind(fd9, \"[fd00::9]:8888\")\nbind(fd10, \"[fd00::10]:8888\")\n\n/* Correctly return -EADDRINUSE because \"hash\" is used\n * instead of \"hash2\". udp_lib_lport_inuse() detects the\n * conflict.\n */\nbind(fail_fd, \"[::]:8888\")\n\n/* After one more socket is bound to \"[fd00::11]:8888\",\n * hslot-\u003ecount exceeds 10 and \"hash2\" is used instead.\n */\nbind(fd11, \"[fd00::11]:8888\")\nbind(fail_fd, \"[::]:8888\") /* succeeds unexpectedly */\n\nThe same issue applies to the IPv4 wildcard address \"0.0.0.0\"\nand the IPv4-mapped wildcard address \"::ffff:0.0.0.0\". For\nexample, if there are existing sockets bound to\n\"192.168.1.[1-11]:8888\", then binding \"0.0.0.0:8888\" or\n\"[::ffff:0.0.0.0]:8888\" can also miss the conflict when\nhslot-\u003ecount \u003e 10.\n\nTCP inet_csk_get_port() already has the correct check in\ninet_use_bhash2_on_bind(). Rename it to\ninet_use_hash2_on_bind() and move it to inet_hashtables.h\nso udp.c can reuse it in this fix."
}
],
"providerMetadata": {
"dateUpdated": "2026-04-22T13:54:23.221Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/d6ace0dbcbb7fd285738bb87b42b71b01858c952"
},
{
"url": "https://git.kernel.org/stable/c/2297e38114316b26ae02f2d205c49b5511c5ed55"
},
{
"url": "https://git.kernel.org/stable/c/f1bed05a832ae79be5f7a105da56810eaa59a5f1"
},
{
"url": "https://git.kernel.org/stable/c/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4"
},
{
"url": "https://git.kernel.org/stable/c/0a360f7f73a06ac88f18917055fbcc79694252d7"
},
{
"url": "https://git.kernel.org/stable/c/e537dd15d0d4ad989d56a1021290f0c674dd8b28"
}
],
"title": "udp: Fix wildcard bind conflict check when using hash2",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-31503",
"datePublished": "2026-04-22T13:54:23.221Z",
"dateReserved": "2026-03-09T15:48:24.105Z",
"dateUpdated": "2026-04-22T13:54:23.221Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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