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CVE Record

CVE-2021-47479: staging: rtl8712: fix use-after-free in rtl8712_dl_fw

In the Linux kernel, the following vulnerability has been resolved: staging: rtl8712: fix use-after-free in rtl8712_dl_fw Syzbot reported use-after-free in rtl8712_dl_fw(). The problem was in race condition between r871xu_dev_remove() ->ndo_open() callback. It's easy to see from crash log, that driver accesses released firmware in ->ndo_open() callback. It may happen, since driver was releasing firmware _before_ unregistering netdev. Fix it by moving unregister_netdev() before cleaning up resources. Call Trace: ... rtl871x_open_fw drivers/staging/rtl8712/hal_init.c:83 [inline] rtl8712_dl_fw+0xd95/0xe10 drivers/staging/rtl8712/hal_init.c:170 rtl8712_hal_init drivers/staging/rtl8712/hal_init.c:330 [inline] rtl871x_hal_init+0xae/0x180 drivers/staging/rtl8712/hal_init.c:394 netdev_open+0xe6/0x6c0 drivers/staging/rtl8712/os_intfs.c:380 __dev_open+0x2bc/0x4d0 net/core/dev.c:1484 Freed by task 1306: ... release_firmware+0x1b/0x30 drivers/base/firmware_loader/main.c:1053 r871xu_dev_remove+0xcc/0x2c0 drivers/staging/rtl8712/usb_intf.c:599 usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:458

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-47479 is a Linux kernel bug in the staging rtl8712 wireless driver. A race during device removal and network-device open can leave the driver using firmware memory after it was released. The source bundle does not provide a CVSS score or evidence of active exploitation.

Executive priority

Handle through normal kernel patch governance unless rtl8712 hardware is present in sensitive or exposed environments. There is no sourced active exploitation signal, but kernel memory-safety bugs can affect availability and system trust boundaries.

Technical view

The flaw is a use-after-free in rtl8712_dl_fw(). r871xu_dev_remove() released firmware before unregistering the network device, allowing an ndo_open path to access freed firmware. The kernel fix moves unregister_netdev() before resource cleanup. Affected status depends on kernel version and whether the rtl8712 staging driver is present and reachable.

Likely exposure

Exposure is most likely on Linux systems running affected kernels with the staging rtl8712 driver for supported Realtek USB wireless hardware. Servers without this driver or hardware are less likely exposed. The source bundle’s affected version data is limited and should be verified against distribution kernel backports.

Exploitation context

The bundle attributes discovery to syzbot and shows a kernel crash trace. It does not cite public exploitation, weaponized proof of concept, or CISA KEV inclusion. Treat exploitation status as not established from the provided evidence.

Researcher notes

Key condition is the race between r871xu_dev_remove() cleanup and ndo_open. Validation should focus on fix presence, driver availability, and practical device reachability. The provided data lacks CVSS, CWE, exploitability analysis, and distribution-specific advisory coverage.

Mitigation direction

  • Apply vendor or distribution kernel updates containing the referenced stable fixes.
  • Verify whether your distribution backported the rtl8712 cleanup-order fix.
  • If updates are unavailable, follow vendor guidance for temporary controls.
  • Prioritize systems using Realtek rtl8712 USB wireless devices or staging drivers.

Validation and detection

  • Inventory Linux kernel versions and distribution patch levels.
  • Check whether the rtl8712 driver is built, loaded, or packaged.
  • Confirm the referenced stable commits appear in kernel source or changelog.
  • Review crash telemetry for rtl8712 firmware or netdev open/remove faults.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2021-47479 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
5Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux8c213fa59199f9673d66970d6940fa093186642f, 8c213fa59199f9673d66970d6940fa093186642f, 8c213fa59199f9673d66970d6940fa093186642f, 8c213fa59199f9673d66970d6940fa093186642f, bc5d453eab4506cb52397db8830d1070904265a4unaffected
LinuxLinux3.3, 0, 5.10.79, 5.14.18, 5.15.2, 5.16affected
Weakness

CWE details

No CWE listed

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