CVE-2026-45251 (GCVE-0-2026-45251)
Vulnerability from cvelistv5 – Published: 2026-05-21 09:04 – Updated: 2026-05-21 09:04
VLAI?
Title
Kernel use-after-free via file descriptor syscalls
Summary
A file descriptor can be closed while a thread is blocked in a poll(2) or select(2) call waiting for that descriptor. Because the blocked thread does not hold a reference to the underlying object, this closure may result in the object being freed while the thread remains blocked. In this situation, the kernel must remove the blocked thread from the per-object wait queue prior to freeing the object.
In the case of some file descriptor types, the kernel failed to unlink blocked threads from the object before freeing it. When the blocked thread is subsequently woken, it accesses memory that has already been freed resulting in a use-after-free vulnerability.
The use-after-free vulnerability may be triggered by an unprivileged local user and can be exploited to obtain superuser privileges.
Severity ?
No CVSS data available.
CWE
- CWE-416 - Use After Free
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://security.freebsd.org/advisories/FreeBSD-S… | vendor-advisory |
Impacted products
Date Public ?
2026-05-20 23:00
Credits
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unknown",
"modules": [
"file"
],
"product": "FreeBSD",
"vendor": "FreeBSD",
"versions": [
{
"lessThan": "p9",
"status": "affected",
"version": "15.0-RELEASE",
"versionType": "release"
},
{
"lessThan": "p5",
"status": "affected",
"version": "14.4-RELEASE",
"versionType": "release"
},
{
"lessThan": "p14",
"status": "affected",
"version": "14.3-RELEASE",
"versionType": "release"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "75Acol, Lexpl0it, fcgboy, and robinzeng2015"
},
{
"lang": "en",
"type": "finder",
"value": "Ryan at Calif.io"
}
],
"datePublic": "2026-05-20T23:00:00.000Z",
"descriptions": [
{
"lang": "en",
"value": "A file descriptor can be closed while a thread is blocked in a poll(2) or select(2) call waiting for that descriptor. Because the blocked thread does not hold a reference to the underlying object, this closure may result in the object being freed while the thread remains blocked. In this situation, the kernel must remove the blocked thread from the per-object wait queue prior to freeing the object.\n\nIn the case of some file descriptor types, the kernel failed to unlink blocked threads from the object before freeing it. When the blocked thread is subsequently woken, it accesses memory that has already been freed resulting in a use-after-free vulnerability.\n\nThe use-after-free vulnerability may be triggered by an unprivileged local user and can be exploited to obtain superuser privileges."
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-416",
"description": "CWE-416: Use After Free",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-21T09:04:52.569Z",
"orgId": "63664ac6-956c-4cba-a5d0-f46076e16109",
"shortName": "freebsd"
},
"references": [
{
"tags": [
"vendor-advisory"
],
"url": "https://security.freebsd.org/advisories/FreeBSD-SA-26:19.file.asc"
}
],
"title": "Kernel use-after-free via file descriptor syscalls",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "63664ac6-956c-4cba-a5d0-f46076e16109",
"assignerShortName": "freebsd",
"cveId": "CVE-2026-45251",
"datePublished": "2026-05-21T09:04:52.569Z",
"dateReserved": "2026-05-11T16:27:44.891Z",
"dateUpdated": "2026-05-21T09:04:52.569Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-45251\",\"sourceIdentifier\":\"secteam@freebsd.org\",\"published\":\"2026-05-21T10:16:26.043\",\"lastModified\":\"2026-05-21T10:16:26.043\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"A file descriptor can be closed while a thread is blocked in a poll(2) or select(2) call waiting for that descriptor. Because the blocked thread does not hold a reference to the underlying object, this closure may result in the object being freed while the thread remains blocked. In this situation, the kernel must remove the blocked thread from the per-object wait queue prior to freeing the object.\\n\\nIn the case of some file descriptor types, the kernel failed to unlink blocked threads from the object before freeing it. When the blocked thread is subsequently woken, it accesses memory that has already been freed resulting in a use-after-free vulnerability.\\n\\nThe use-after-free vulnerability may be triggered by an unprivileged local user and can be exploited to obtain superuser privileges.\"}],\"metrics\":{},\"weaknesses\":[{\"source\":\"secteam@freebsd.org\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-416\"}]}],\"references\":[{\"url\":\"https://security.freebsd.org/advisories/FreeBSD-SA-26:19.file.asc\",\"source\":\"secteam@freebsd.org\"}]}}"
}
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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