Use-after-free in TCP RACK stack option handler
Summary
| CVE | CVE-2026-49422 |
|---|---|
| State | PUBLISHED |
| Assigner | freebsd |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-19 06:17:41 UTC |
| Updated | 2026-09-01 20:20:00 UTC |
| Description | The RACK setsockopt(2) handler drops the connection lock in order to copy option data from userspace, then reacquires the lock. After reacquiring, it verifies that the TCP stack had not been switched away, but did not reload its pointer to the stack's per-connection control block. If userspace switches stacks twice during this window, the check will succeed but the saved pointer will refer to freed memory. The bug may be exploitable by an unprivileged local user to escalate privileges. |
Risk And Classification
Primary CVSS: v3.1 8.4 HIGH from ADP
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS: 0.001260000 probability, percentile 0.025470000 (date 2026-09-03)
Problem Types: CWE-416 | CWE-416 CWE-416: Use After Free
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | DECLARED | 8.4 | HIGH | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| 3.1 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | Secondary | 8.4 | HIGH | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
CVSS v3.1 Breakdown
Attack Vector
LocalAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Operating System | Freebsd | Freebsd | 14.3 | - | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p1 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p10 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p11 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p12 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p13 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p14 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p15 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p2 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p3 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p4 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p5 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p6 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p7 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p8 | All | All |
| Operating System | Freebsd | Freebsd | 14.3 | p9 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | - | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | p1 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | p2 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | p3 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | p4 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | p5 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | p6 | All | All |
| Operating System | Freebsd | Freebsd | 14.4 | rc1 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | - | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p1 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p10 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p2 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p3 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p4 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p5 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p6 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p7 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p8 | All | All |
| Operating System | Freebsd | Freebsd | 15.0 | p9 | All | All |
| Operating System | Freebsd | Freebsd | 15.1 | - | All | All |
| Operating System | Freebsd | Freebsd | 15.1 | rc2 | All | All |
| Operating System | Freebsd | Freebsd | 15.1 | rc3-p1 | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | FreeBSD | FreeBSD | affected 15.1-RELEASE p1 release | Not specified |
| CNA | FreeBSD | FreeBSD | affected 15.0-RELEASE p11 release | Not specified |
| CNA | FreeBSD | FreeBSD | affected 14.4-RELEASE p7 release | Not specified |
| CNA | FreeBSD | FreeBSD | affected 14.3-RELEASE p16 release | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| security.freebsd.org/advisories/FreeBSD-SA-26:43.tcp.asc | [email protected] | security.freebsd.org | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Maik Muench (en)
There are currently no legacy QID mappings associated with this CVE.