CVE-2026-63821
In the Linux kernel, the following vulnerability has been resolved:
wifi: rtw88: usb: fix memory leaks on USB write failures
When rtw_usb_write_port() fails to submit a USB Request Block (URB)
(e.g., due to device disconnect or ENOMEM), the completion callback is
never executed.
Currently, the driver ignores the return value of rtw_usb_write_port()
in rtw_usb_write_data() and rtw_usb_tx_agg_skb(). Because these
functions rely on the completion callback to free the socket buffers
(skbs) and the transaction control block (txcb), a submission failure
results in:
1. A memory leak of the allocated skb in rtw_usb_write_data().
2. A memory leak of the txcb structure and all aggregated skbs in
rtw_usb_tx_agg_skb().
Fix this by checking the return value of rtw_usb_write_port(). If it
fails, explicitly free the skb in rtw_usb_write_data(), and properly
purge the tx_ack_queue and free the txcb in rtw_usb_tx_agg_skb().
The issue was discovered in practice during device disconnect/reconnect
scenarios and memory pressure conditions. Tested by verifying normal TX
operation continues after the fix without regressions.
CSIRTS triage
- What
- The vulnerability fixes memory leaks on USB write failures in the rtw88 driver.
- Who is affected
- Deployments of KVM that use the rtw88 USB Wi-Fi driver.
- Urgency
- Remediation is necessary to prevent resource exhaustion.
- Action
- Update to the latest version of KVM.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.16% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 5% of all EPSS-scored CVEs.
Advisory coverage (2)
- unknownCVE-2026-63821: In the Linux kernel, the following vulnerability has been resolved: wifi: rtw88: usb: fix memo…nvd · 2026-07-19
- mediumCVE-2026-63821: wifi: rtw88: usb: fix memory leaks on USB write failuresmsrc · 2026-07-14
External references
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