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CVE-2026-49419 FreeBSD CVE debrief

An unprivileged local user can trigger a prison reference count underflow via the JAIL_AT_DESC flag in kern_jail_set() and kern_jail_get(), potentially causing a panic or privilege escalation. This vulnerability affects FreeBSD systems, allowing an attacker to exploit improper handling of prison references, leading to a potential underflow in the reference count. The bug may result in an immediate panic on the jail host, but if the user is running in a jail, it may be possible to exploit the bug to elevate privileges. System administrators should review system configurations, monitor system logs, and prioritize patching to mitigate this vulnerability.

Vendor
FreeBSD
Product
Unknown
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-19
Original CVE updated
2026-08-26
Advisory published
2026-08-19
Advisory updated
2026-08-26

Who should care

System administrators and users of FreeBSD systems should be aware of this vulnerability and take steps to mitigate it. This includes reviewing system configurations, monitoring system logs, and prioritizing patching. Additionally, security teams and vulnerability management teams should review the vulnerability and assess its impact on their systems and operations.

Technical summary

The JAIL_AT_DESC flag in kern_jail_set() and kern_jail_get() can be exploited by an unprivileged local user to trigger a prison reference count underflow, potentially causing a panic or privilege escalation. This vulnerability affects FreeBSD systems and may allow for local privilege escalation. The technical details of the vulnerability involve the improper handling of prison references, leading to a potential underflow in the reference count.

Defensive priority

High-priority patching recommended due to potential for local privilege escalation.

Recommended defensive actions

  • Apply patch from vendor
  • Verify system configuration
  • Monitor system logs
  • Review compensating controls for exposed systems
  • Check relevant monitoring, detection, and logs for exposed assets
  • Track exceptions and retest remediated assets
  • Confirm whether affected product deployments exist in managed environments

Evidence notes

Evidence from FreeBSD security advisory and NVD vulnerability detail page supports the existence of the vulnerability. The FreeBSD advisory provides details on the JAIL_AT_DESC flag and its impact on prison reference counts. However, the scope of affected systems and potential exploitation vectors is still being verified. Defenders should review system configurations, monitor for suspicious activity, and prioritize patching. Additional evidence and context are needed to fully understand the vulnerability's impact.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-49419 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-49419

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-49419 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-49419

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.