Bug 2540380 (CVE-2026-93805) - CVE-2026-93805 kernel: wifi: cfg80211: validate rx/tx MLME callback frame lengths before access
Summary: CVE-2026-93805 kernel: wifi: cfg80211: validate rx/tx MLME callback frame len...
Keywords:
Status: NEW
Alias: CVE-2026-93805
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-24 16:35 UTC by OSIDB Bzimport
Modified: 2026-09-28 12:43 UTC (History)
17 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-09-24 16:35:51 UTC
In the Linux kernel, the following vulnerability has been resolved:

wifi: cfg80211: validate rx/tx MLME callback frame lengths before access

cfg80211_rx_mlme_mgmt() and cfg80211_tx_mlme_mgmt() call tracepoints
before rejecting frames shorter than the frame-control field. After
that, they only require len >= 2 before dispatching into subtype
handlers that assume their fixed fields are present.

The frames that trip this are not shorter than 2 bytes; they are short
relative to their subtype. mwifiex is a concrete in-tree example on the
length side: mwifiex_process_mgmt_packet() only requires a 4-address
ieee80211_hdr plus the 2-byte firmware length prefix before handing the
frame to cfg80211_rx_mlme_mgmt(). After stripping the length prefix and
removing addr4, pkt_len can be exactly 24: a bare 3-address management
header with no reason-code body. The existing WARN_ON(len < 2) does not
fire on such a frame, and cfg80211_process_deauth() then reads
u.deauth.reason_code as a two-byte access starting at offset 24,
immediately past the 24-byte buffer.

Add a frame-control length gate, then validate each subtype's minimum
frame size in an if/else-if chain that mirrors the dispatch logic. Trace
only after the frame is known to be well-formed.

Side effects of this change:
 - The WARN_ON(len < 2) is dropped. It only guarded the frame_control
   read, never the subtype fixed fields, and it does not fire on the
   frames that actually trigger the out-of-bounds read (which are >= 2).
   The len >= 2 check is kept as the guard before dereferencing
   frame_control, but without the warning: these are exported callbacks
   and a malformed frame from a driver should be dropped silently rather
   than backtraced.
 - cfg80211_tx_mlme_mgmt() previously routed every non-deauth subtype
   through disassociation handling; it now silently ignores unrecognised
   subtypes.


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