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CVE-2026-14366· NVD / CVE Program· CNA zephyr

SiWx91x WiFi driver double-unref / use-after-free of caller-owned TX net_pkt

The Silicon Labs SiWx917 WiFi driver's transmit callback siwx91x_send() in drivers/wifi/siwx91x/siwx91x_wifi.c frees a network packet it does not own. In the Zephyr TX path the net_pkt is owned by the L2/networking stack; the driver only borrows it to copy the frame bytes into a local net_buf. Before the fix, after transmitting, siwx91x_send() additionally called net_pkt_unref(pkt) on the caller-owned packet, dropping its last reference and returning it to the shared packet pool prematurely. This code path is compiled in by default (CONFIG_WIFI_SILABS_SIWX91X_NET_STACK_NATIVE). The caller, ethernet_send() in subsys/net/l2/ethernet/ethernet.c, keeps using the packet after the driver returns: it reads net_pkt_get_len(pkt), updates TX statistics, and then performs its own net_pkt_unref(pkt). Because the driver already released the packet, these are use-after-free reads followed by a second unref (a double free). When concurrent network activity recycles the freed slab slot between the two unrefs, the trailing unref decrements a different, live packet's reference count and frees it, corrupting the net_pkt pool shared by both the receive and transmit paths. The defect is exercised by ordinary transmission over the native-stack SiWx917 WiFi interface, and an adjacent attacker on the same WiFi network can induce transmissions (for example ARP or ICMP echo replies, or TCP handshakes) to drive the path. The primary observable impact is loss of availability (transmit hangs and crashes from pool corruption), with race-dependent memory corruption of the kernel networking buffer pool. The fix removes the erroneous net_pkt_unref(pkt) from siwx91x_send(); the driver's receive-path unref, which correctly frees a packet the driver itself allocated, is unaffected.

MediumCVSS 6.4 · v3.1—No exploit Fix available
Published
Aug 31, 2026
Updated
Sep 1, 2026
EPSS
0.2% · 5th percentile
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Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
25 / 40 · 6.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · zephyr
6.4
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (zephyr). Independent of NVD's CPE analysis and usually ahead of it.

  • zephyrproject zephyr

    • 4.1.0 and later · before 4.4.2affected · semver

Same product

zephyrproject: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-4260Potential off-by-one buffer overflow vulnerability in the Zephyr FS subsystem
    40Plan
  • CVE-2021-3625Buffer overflow in Zephyr USB DFU DNLOAD
    40Plan
  • CVE-2020-10071Insufficient publish message length validation in MQTT
    40Plan
  • CVE-2020-10070MQTT buffer overflow on receive buffer
    40Plan
  • CVE-2020-10062Packet length decoding error in MQTT
    40Plan
  • CVE-2020-10022UpdateHub Module Copies a Variable-Size Hash String Into a Fixed-Size Array
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
zephyrproject zephyr4.4.2Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1236617 days apartUse-after-free freeing an armed dynamically-allocated k_timer in Zephyr userspace object disposal
    35Monitor
  • CVE-2026-1066750 days apartSMP use-after-free in Zephyr `CONFIG_USERSPACE` dynamic kernel-object tracking, reachable from unprivileged user threads
    31Monitor
  • CVE-2026-1068531 days apartUse-after-free of GATT subscribe params in Bluetooth host CCC-write response handler
    30Monitor
  • CVE-2026-1063876 days apartUse-after-free in Zephyr ICMPv6 RX path when updating statistics after sending an echo reply or error
    30Monitor
  • CVE-2026-1064664 days apartUse-after-return in `zsock_getaddrinfo()` when a timed-out DNS query is retried without cancellation
    29Monitor
  • CVE-2026-1063776 days apartUse-after-free of `net_pkt` in IPv6 MLD send path triggerable by a link-local MLD Query
    28Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone on the same network segment can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Adjacent
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records