CVE-2026-93785: cifs: validate idmap key payload length
In the Linux kernel, the following vulnerability has been resolved:
cifs: validate idmap key payload length
The cifs.idmap key type stores its payload length in key->datalen, which is limited to U16MAX. Accepting a larger key payload truncates the recorded length and can make later users interpret the payload using inconsistent bounds.
Reject oversized preparsed payloads before allocating or copying them. This keeps key->datalen consistent with the stored data for both inline and separately allocated idmap payloads.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
For the cifs.idmap key type, reject oversized preparsed payloads before allocating or copying them, and enforce that key->datalen does not exceed U16_MAX.
Event History
Frequently Asked Questions
What condition is required to trigger the vulnerable behavior?
A cifs.idmap key payload larger than U16_MAX must be accepted during preparsing. The oversized length can be truncated in key->datalen, causing later users to operate with bounds inconsistent with the stored payload.
What is the mitigation when an immediate update is not possible?
The provided data identifies the necessary safeguard: reject oversized preparsed cifs.idmap payloads before they are allocated or copied. No other workaround or configuration-based mitigation is specified.