bpf: Fix bounds check for skb-backed dynptrs
The skb_pointer_if_linear() function checks whether a
memory region of length len starting at offset off into
the skb is in the linear area, and returns a pointer to
the region if so. The check currently subtracts between
skb_headlen and offset of the check, and since skb_headlen
is unsigned the subtraction can underflow. This causes the
bounds check to spuriously pass and generate an arbitrary
pointer of the form *(skb->data + off).
The only user of this helper is currently skb-backed BPF
dynptr code. Returning the wrong pointer leads to the
dynptr erroneously being backed with invalid memory.
Ensure the subtraction cannot underflow, and fail the check if
it would. Use u64 arithmetic to also prevent overflow when
calculating (skb_headlen(skb) - off) since off is unsigned.
Analysis
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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 |
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| Linux | Linux | affected |
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No solution or workaround provided in the CVE record.
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Sun, 18 Oct 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: Fix bounds check for skb-backed dynptrs The skb_pointer_if_linear() function checks whether a memory region of length len starting at offset off into the skb is in the linear area, and returns a pointer to the region if so. The check currently subtracts between skb_headlen and offset of the check, and since skb_headlen is unsigned the subtraction can underflow. This causes the bounds check to spuriously pass and generate an arbitrary pointer of the form *(skb->data + off). The only user of this helper is currently skb-backed BPF dynptr code. Returning the wrong pointer leads to the dynptr erroneously being backed with invalid memory. Ensure the subtraction cannot underflow, and fail the check if it would. Use u64 arithmetic to also prevent overflow when calculating (skb_headlen(skb) - off) since off is unsigned. | |
| Title | bpf: Fix bounds check for skb-backed dynptrs | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-18T15:19:03.567Z
Reserved: 2026-09-25T10:25:14.359Z
Link: CVE-2026-98591
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-18T16:17:11.727
Modified: 2026-10-18T16:17:11.727
Link: CVE-2026-98591
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.