cbcvebase.
CVE-2026-31649
published 2026-04-24

CVE-2026-31649: In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix integer underflow in chain mode The jumbo_frm() chain-mode implementation…

PriorityP351critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
0.46%
37.3th percentile
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 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.

Affected

70 ranges· showing 25
VendorProductVersion rangeFixed in
linuxlinux
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < 513e06735f5be575b409d195822195348b164e48513e06735f5be575b409d195822195348b164e48
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < 275bdf762e82082f064e60a92448fa2ac43cf95b275bdf762e82082f064e60a92448fa2ac43cf95b
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2fa2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < b7b8012193fd98236d7ae05d4b553f010a77b2efb7b8012193fd98236d7ae05d4b553f010a77b2ef
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < 2c91b39912278d0878f9ba60ba04d2518b18a08d2c91b39912278d0878f9ba60ba04d2518b18a08d
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < 6fca757c20396dc2e604dcc61922264e9e3dc8036fca757c20396dc2e604dcc61922264e9e3dc803
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < 10d12b9240ebf96c785f0e2e4228318cd5f3a3eb10d12b9240ebf96c785f0e2e4228318cd5f3a3eb
linuxlinux>= 286a837217204b1ef105e3a554d0757e4fdfaac1 < 51f4e090b9f87b40c21b6daadb5c06e6c0a07b6751f4e090b9f87b40c21b6daadb5c06e6c0a07b67
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel
linuxlinux_kernel>= 3.2.1 < 5.10.2535.10.253
linuxlinux_kernel>= 5.11 < 5.15.2035.15.203
linuxlinux_kernel>= 5.16 < 6.1.1696.1.169
linuxlinux_kernel>= 6.13 < 6.18.236.18.23
linuxlinux_kernel>= 6.19 < 6.19.136.19.13
linuxlinux_kernel>= 6.2 < 6.6.1356.6.135
linuxlinux_kernel>= 6.7 < 6.12.826.12.82

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_ubuntu8.8HIGH
vendor_redhat7.0HIGH
Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.