wifi: mac80211: drop oversized fragments to avoid extra_len overflow

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98829
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:17:37 UTC
Updated2026-10-19 10:19:46 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: drop oversized fragments to avoid extra_len overflow In ieee80211_rx_h_defragment(), fragment payloads are accumulated into entry->extra_len as subsequent fragments arrive: entry->extra_len += rx->skb->len; When the final fragment arrives, the head fragment is dequeued, and pskb_expand_head() is called with entry->extra_len to ensure sufficient tailroom for all queued fragments before copying: if (skb_tailroom(rx->skb) < entry->extra_len) { if (unlikely(pskb_expand_head(rx->skb, 0, entry->extra_len, GFP_ATOMIC))) { ... } } while ((skb = __skb_dequeue(&entry->skb_list))) { skb_put_data(rx->skb, skb->data, skb->len); dev_kfree_skb(skb); } In commit 69f132236827 ("mac80211: shrink struct ieee80211_fragment_entry"), entry->extra_len was narrowed from unsigned int to u16 in order to reduce structure memory footprint. However, an IEEE 802.11 frame sequence can contain up to 16 fragments (frag numbers 0..15). If a sequence of large fragments arrives (e.g. from a malicious peer or rogue AP), the sum of fragment lengths can exceed 65535 bytes (for example, 15 fragments of 4400 bytes total 66000 bytes). Because extra_len is a u16, this addition overflows and wraps around modulo 65536 (e.g. 66000 wraps to 464). Consequently, pskb_expand_head() allocates only the truncated amount of tailroom (or is skipped entirely if the head fragment already has >= 464 bytes of tailroom). When skb_put_data() subsequently iterates through the queued skb list, it appends the full payload into the undersized buffer, causing skb_put() to trigger skb_over_panic() and crash the kernel in softirq context. A legitimate MSDU in IEEE 802.11 is at most 2304 bytes (or up to 7935/11454 bytes for A-MSDU, which is not fragmented), well below U16_MAX. Fix this without increasing the size of struct ieee80211_fragment_entry by checking whether adding the incoming fragment length would exceed U16_MAX. If so, purge the queued fragments and drop the frame. [assign a separate drop reason]

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 69f132236827ce7d4531846cc2b9447dd5620aff 9338b2dea74cb0fc80a4c958b68e687610ba2261 git Not specified
CNA Linux Linux affected 69f132236827ce7d4531846cc2b9447dd5620aff 870b8cb9baa9bd859deceb33ae158011e6ba2360 git Not specified
CNA Linux Linux affected 69f132236827ce7d4531846cc2b9447dd5620aff 5e4f3509793b4db2c0835340224743db680e861f git Not specified
CNA Linux Linux affected 4.3 Not specified
CNA Linux Linux unaffected 4.3 semver Not specified
CNA Linux Linux unaffected 6.18.56 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.10 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/5e4f3509793b4db2c0835340224743db680e861f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9338b2dea74cb0fc80a4c958b68e687610ba2261 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/870b8cb9baa9bd859deceb33ae158011e6ba2360 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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