CVE-2026-31649
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BaseFortify
Publication date: 2026-04-24
Last updated on: 2026-04-27
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
net: stmmac: fix integer underflow in chain mode
The jumbo_frm() chain-mode implementation unconditionally computes
len = nopaged_len - bmax;
where nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is
BUF_SIZE_8KiB or BUF_SIZE_2KiB. However, the caller stmmac_xmit()
decides to invoke jumbo_frm() based on skb->len (total length including
page fragments):
is_jumbo = stmmac_is_jumbo_frm(priv, skb->len, enh_desc);
When a packet has a small linear portion (nopaged_len <= bmax) but a
large total length due to page fragments (skb->len > bmax), the
subtraction wraps as an unsigned integer, producing a huge len value
(~0xFFFFxxxx). This causes the while (len != 0) loop to execute
hundreds of thousands of iterations, passing skb->data + bmax * i
pointers far beyond the skb buffer to dma_map_single(). On IOMMU-less
SoCs (the typical deployment for stmmac), this maps arbitrary kernel
memory to the DMA engine, constituting a kernel memory disclosure and
potential memory corruption from hardware.
Fix this by introducing a buf_len local variable clamped to
min(nopaged_len, bmax). Computing len = nopaged_len - buf_len is then
always safe: it is zero when the linear portion fits within a single
descriptor, causing the while (len != 0) loop to be skipped naturally,
and the fragment loop in stmmac_xmit() handles page fragments afterward.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| linux | linux_kernel | 3.2 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | 7.0 |
| linux | linux_kernel | From 5.11 (inc) to 5.15.203 (exc) |
| linux | linux_kernel | From 3.2.1 (inc) to 5.10.253 (exc) |
| linux | linux_kernel | From 5.16 (inc) to 6.1.169 (exc) |
| linux | linux_kernel | From 6.13 (inc) to 6.18.23 (exc) |
| linux | linux_kernel | From 6.19 (inc) to 6.19.13 (exc) |
| linux | linux_kernel | From 6.2 (inc) to 6.6.135 (exc) |
| linux | linux_kernel | From 6.7 (inc) to 6.12.82 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-190 | The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number. |
Attack-Flow Graph
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