CVE-2026-49419 (GCVE-0-2026-49419)
Vulnerability from cvelistv5 – Published: 2026-08-19 04:32 – Updated: 2026-08-19 04:32
VLAI
EPSS
VEX
Title
Jail reference count underflow
Summary
When the JAIL_AT_DESC flag is specified, kern_jail_set() and kern_jail_get() released the reference to the caller's current prison before looking up the jail descriptor. If the descriptor lookup failed, error-handling paths released the same reference a second time.
An unprivileged local user can trigger a prison reference count underflow, which may cause the prison structure to be freed while still in use. When this is done on the jail host, the bug will generally result in an immediate panic. However, if the user is running in a jail, then it may be possible to exploit the bug to elevate privileges.
Severity
No CVSS data available.
CWE
- CWE-911 - Improper Update of Reference Count
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://security.freebsd.org/advisories/FreeBSD-S… | vendor-advisory |
Impacted products
Date Public
2026-06-30 20:00
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unknown",
"modules": [
"jail"
],
"product": "FreeBSD",
"vendor": "FreeBSD",
"versions": [
{
"lessThan": "p1",
"status": "affected",
"version": "15.1-RELEASE",
"versionType": "release"
},
{
"lessThan": "p11",
"status": "affected",
"version": "15.0-RELEASE",
"versionType": "release"
}
]
}
],
"credits": [
{
"lang": "en",
"type": "finder",
"value": "Yuxiang Yang, Yizhou Zhao, Ao Wang, Xuewei Feng, Qi Li, and Ke Xu from Tsinghua University using GLM-5.1 from Z.ai"
}
],
"datePublic": "2026-06-30T20:00:00.000Z",
"descriptions": [
{
"lang": "en",
"value": "When the JAIL_AT_DESC flag is specified, kern_jail_set() and kern_jail_get() released the reference to the caller\u0027s current prison before looking up the jail descriptor. If the descriptor lookup failed, error-handling paths released the same reference a second time.\n\nAn unprivileged local user can trigger a prison reference count underflow, which may cause the prison structure to be freed while still in use. When this is done on the jail host, the bug will generally result in an immediate panic. However, if the user is running in a jail, then it may be possible to exploit the bug to elevate privileges."
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-911",
"description": "CWE-911: Improper Update of Reference Count",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T04:32:39.446Z",
"orgId": "63664ac6-956c-4cba-a5d0-f46076e16109",
"shortName": "freebsd"
},
"references": [
{
"tags": [
"vendor-advisory"
],
"url": "https://security.freebsd.org/advisories/FreeBSD-SA-26:38.jail.asc"
}
],
"title": "Jail reference count underflow",
"x_generator": {
"engine": "cvelib 1.8.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "63664ac6-956c-4cba-a5d0-f46076e16109",
"assignerShortName": "freebsd",
"cveId": "CVE-2026-49419",
"datePublished": "2026-08-19T04:32:39.446Z",
"dateReserved": "2026-05-29T20:24:28.616Z",
"dateUpdated": "2026-08-19T04:32:39.446Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-49419\",\"sourceIdentifier\":\"secteam@freebsd.org\",\"published\":\"2026-08-19T05:17:04.053\",\"lastModified\":\"2026-08-19T05:17:04.053\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"When the JAIL_AT_DESC flag is specified, kern_jail_set() and kern_jail_get() released the reference to the caller\u0027s current prison before looking up the jail descriptor. If the descriptor lookup failed, error-handling paths released the same reference a second time.\\n\\nAn unprivileged local user can trigger a prison reference count underflow, which may cause the prison structure to be freed while still in use. When this is done on the jail host, the bug will generally result in an immediate panic. However, if the user is running in a jail, then it may be possible to exploit the bug to elevate privileges.\"}],\"affected\":[{\"source\":\"secteam@freebsd.org\",\"affectedData\":[{\"vendor\":\"FreeBSD\",\"product\":\"FreeBSD\",\"defaultStatus\":\"unknown\",\"modules\":[\"jail\"],\"versions\":[{\"version\":\"15.1-RELEASE\",\"lessThan\":\"p1\",\"versionType\":\"release\",\"status\":\"affected\"},{\"version\":\"15.0-RELEASE\",\"lessThan\":\"p11\",\"versionType\":\"release\",\"status\":\"affected\"}]}]}],\"metrics\":{},\"weaknesses\":[{\"source\":\"secteam@freebsd.org\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-911\"}]}],\"references\":[{\"url\":\"https://security.freebsd.org/advisories/FreeBSD-SA-26:38.jail.asc\",\"source\":\"secteam@freebsd.org\"}]}}"
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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