EUVD-2026-62231
GHSA-w2h3-c2wj-whwm
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local syscall vector, high complexity for UAF exploitation, low privilege (any user), scope changed on jail escape to host.
Primary rating from Vendor (freebsd).
CVSS VectorVendor: freebsd
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
4DescriptionCVE.org
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.
AnalysisAI
Reference count underflow in FreeBSD's jail subsystem allows an unprivileged local user to double-free a prison structure, yielding two distinct impact paths: on the jail host, this reliably causes an immediate kernel panic, while a user already running inside a jail may be able to exploit the freed structure while still in use to escape the jail and elevate privileges to the host. Affected releases are FreeBSD 15.0-RELEASE before patch level 11 and FreeBSD 15.1-RELEASE before patch level 1, per FreeBSD Security Advisory SA-26:38. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The vulnerability is triggered only when the JAIL_AT_DESC flag is explicitly passed to the jail(2) syscall family (kern_jail_set or kern_jail_get), and only when the subsequent jail descriptor lookup fails - an error condition the attacker can deliberately engineer by passing an invalid descriptor. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The provided CVSS 3.1 score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) conflicts with several aspects of the description and warrants scrutiny. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a low-privilege shell account inside a FreeBSD jail passes a crafted JAIL_AT_DESC descriptor to kern_jail_get() or kern_jail_set(), deliberately causing the descriptor lookup to fail. The double-release drives the current prison's reference count below zero, and the allocator frees the prison structure. … |
| Remediation | The primary remediation is to upgrade to FreeBSD 15.0-RELEASE-p11 or FreeBSD 15.1-RELEASE-p1, which contain the fix addressing the double-release in the JAIL_AT_DESC error path. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all FreeBSD 15.0-RELEASE (pre-patch level 11) and 15.1-RELEASE (pre-patch level 1) systems, identifying active jail deployments and local user access patterns. …
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External POC / Exploit Code
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