CVE-2026-98829
wifi: mac80211: drop oversized fragments to avoid extra_len overflow
Published Oct 18, 2026
CVSS 3.1 · 6.5 Medium
EPSS < 1%
KEV · Not listed
Description
In 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]
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]
Affected Products
-
CVE record
-
NVD configurations
No data
-
Red Hat packages
No data
-
OpenCVE enrichment
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
| Vendor | Product | Versions | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux Kernel |
|
||||||||||||||||||||||||
| Linux | Linux Kernel |
|
Remediation
Tracking
Advisories
| Source | ID | Title |
|---|---|---|
 Ubuntu USN |
USN-9018-1 | Linux kernel vulnerabilities |
| Ubuntu USN |
USN-9018-2 | Linux kernel (HWE) vulnerabilities |
| Ubuntu USN |
USN-9019-1 | Linux kernel (Azure) vulnerabilities |
| Ubuntu USN |
USN-9020-1 | Linux kernel vulnerabilities |
Metrics
No CVSS v4.0
Attack Vector Adjacent Network
Attack Complexity Low
Privileges Required None
Scope Unchanged
Confidentiality Impact None
Integrity Impact None
Availability Impact High
User Interaction None
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.166% probability within 30 days)
Key SSVC decision points have not yet been added.
References
History
Oct 24, 2026 2:45 AM
Weaknesses updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-680 |
Oct 24, 2026 12:30 AM
Weaknesses updated. Added references. Scoring metrics updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-190 | |
| References |
| |
| Metrics |
threat_severity
|
cvssV3_1
|
Oct 18, 2026 10:15 PM
Weaknesses updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-680 |
Oct 18, 2026 4:00 PM
Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In 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] | |
| Title | wifi: mac80211: drop oversized fragments to avoid extra_len overflow | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Subscriptions
Weaknesses
