CVE-2026-74488 wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames

What is CVE-2026-74488?

CVE-2026-74488 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

wifi: mwifiex: use the subframe length when parsing A-MSDU TDLS frames

mwifiex_11n_dispatch_amsdu_pkt() splits an A-MSDU with ieee80211_amsdu_to_8023s() and walks the resulting subframes. For each subframe it passes the subframe data pointer to mwifiex_process_tdls_action_frame(), but pairs it with skb->len, the length of the A-MSDU parent, instead of rx_skb->len:

rx_skb = __skb_dequeue(&list); rx_hdr = (struct rx_packet_hdr *)rx_skb->data; if (ISSUPP_TDLS_ENABLED(priv->adapter->fw_cap_info) && ntohs(rx_hdr->eth803_hdr.h_proto) == ETH_P_TDLS) { mwifiex_process_tdls_action_frame(priv, (u8 *)rx_hdr, skb->len); }

The parent is not a valid description of that buffer, and may not be valid memory at all. ieee80211_amsdu_to_8023s() ends with

if (!reuse_skb) dev_kfree_skb(skb);

and it only sets reuse_skb when the parent is linear, is not a head_frag, and is being consumed as the *last* subframe. So when the parent does not qualify for reuse it has already been freed, and the read of skb->len is a use-after-free. When it is reused, skb->len is the length of the last subframe, applied to every earlier subframe, which over-states the buffer whenever an earlier subframe is shorter.

The callee cannot absorb a wrong length, because it derives its own ceiling from the value it is given. Each frame type computes

ies_len = len - sizeof(struct ethhdr) - TDLS_*_FIX_LEN;

and the element walk is then bounded entirely against that ceiling,

for (end = pos + ies_len; pos + 1 < end; pos += 2 + pos[1]) { u8 ie_len = pos[1];

if (pos + 2 + ie_len > end) break;

so a too-large len moves end past the end of the subframe and the walk reads and copies beyond it. The A-MSDU layout is chosen by the sender, which makes the difference between the last subframe and a shorter earlier one remotely selectable. Reaching this requires TDLS support in firmware and the TDLS ethertype on the subframe.

The other caller, mwifiex_process_rx_packet(), is correct: it passes a pointer and a length that describe the same region of the RX buffer.

Pass rx_skb->len, the length of the subframe actually being parsed.

Which versions are affected by CVE-2026-74488?

How do I fix CVE-2026-74488?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2026-74488 being exploited?

There is no known exploitation of CVE-2026-74488 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-96240, BELL-CVE-2026-74488, DEBIAN-CVE-2026-74488, GHSA-c488-ccg3-wfcm, UBUNTU-CVE-2026-74488.