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CVE-2026-31649

net: stmmac: fix integer underflow in chain mode

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in 513e06735f5be575b409d195822195348b164e48; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in 275bdf762e82082f064e60a92448fa2ac43cf95b; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in b7b8012193fd98236d7ae05d4b553f010a77b2ef; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in 2c91b39912278d0878f9ba60ba04d2518b18a08d; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in 6fca757c20396dc2e604dcc61922264e9e3dc803; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in 10d12b9240ebf96c785f0e2e4228318cd5f3a3eb; From 286a837217204b1ef105e3a554d0757e4fdfaac1 · fixed in 51f4e090b9f87b40c21b6daadb5c06e6c0a07b67

  • Linux Linux

    3.2

  • KernelLinux

    From 3.2.0 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.169; From 6.2.0 · fixed in 6.6.135; From 6.7.0 · fixed in 6.12.82; From 6.13.0 · fixed in 6.18.23; From 6.19.0 · fixed in 6.19.13

References 8

git.kernel.org