CVE-2026-31649 (GCVE-0-2026-31649)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:45 – Updated: 2026-04-24 14:45
VLAI?
Title
net: stmmac: fix integer underflow in chain mode
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < 513e06735f5be575b409d195822195348b164e48 (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < 275bdf762e82082f064e60a92448fa2ac43cf95b (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < b7b8012193fd98236d7ae05d4b553f010a77b2ef (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < 2c91b39912278d0878f9ba60ba04d2518b18a08d (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < 6fca757c20396dc2e604dcc61922264e9e3dc803 (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < 10d12b9240ebf96c785f0e2e4228318cd5f3a3eb (git)
Affected: 286a837217204b1ef105e3a554d0757e4fdfaac1 , < 51f4e090b9f87b40c21b6daadb5c06e6c0a07b67 (git)
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    Linux Linux Affected: 3.2
Unaffected: 0 , < 3.2 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.169 , ≤ 6.1.* (semver)
Unaffected: 6.6.135 , ≤ 6.6.* (semver)
Unaffected: 6.12.82 , ≤ 6.12.* (semver)
Unaffected: 6.18.23 , ≤ 6.18.* (semver)
Unaffected: 6.19.13 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/ethernet/stmicro/stmmac/chain_mode.c"
          ],
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          "vendor": "Linux",
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              "version": "3.2"
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              "version": "0",
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              "status": "unaffected",
              "version": "5.10.253",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.169",
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              "lessThanOrEqual": "6.6.*",
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              "status": "unaffected",
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              "status": "unaffected",
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              "status": "unaffected",
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              "versionType": "semver"
            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: stmmac: fix integer underflow in chain mode\n\nThe jumbo_frm() chain-mode implementation unconditionally computes\n\n    len = nopaged_len - bmax;\n\nwhere nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is\nBUF_SIZE_8KiB or BUF_SIZE_2KiB.  However, the caller stmmac_xmit()\ndecides to invoke jumbo_frm() based on skb-\u003elen (total length including\npage fragments):\n\n    is_jumbo = stmmac_is_jumbo_frm(priv, skb-\u003elen, enh_desc);\n\nWhen a packet has a small linear portion (nopaged_len \u003c= bmax) but a\nlarge total length due to page fragments (skb-\u003elen \u003e bmax), the\nsubtraction wraps as an unsigned integer, producing a huge len value\n(~0xFFFFxxxx).  This causes the while (len != 0) loop to execute\nhundreds of thousands of iterations, passing skb-\u003edata + bmax * i\npointers far beyond the skb buffer to dma_map_single().  On IOMMU-less\nSoCs (the typical deployment for stmmac), this maps arbitrary kernel\nmemory to the DMA engine, constituting a kernel memory disclosure and\npotential memory corruption from hardware.\n\nFix this by introducing a buf_len local variable clamped to\nmin(nopaged_len, bmax).  Computing len = nopaged_len - buf_len is then\nalways safe: it is zero when the linear portion fits within a single\ndescriptor, causing the while (len != 0) loop to be skipped naturally,\nand the fragment loop in stmmac_xmit() handles page fragments afterward."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-24T14:45:02.520Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/a2b68a9a476b9544ff31f1fbcd5d80867a8a5e2f"
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          "url": "https://git.kernel.org/stable/c/b7b8012193fd98236d7ae05d4b553f010a77b2ef"
        },
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          "url": "https://git.kernel.org/stable/c/2c91b39912278d0878f9ba60ba04d2518b18a08d"
        },
        {
          "url": "https://git.kernel.org/stable/c/6fca757c20396dc2e604dcc61922264e9e3dc803"
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        {
          "url": "https://git.kernel.org/stable/c/10d12b9240ebf96c785f0e2e4228318cd5f3a3eb"
        },
        {
          "url": "https://git.kernel.org/stable/c/51f4e090b9f87b40c21b6daadb5c06e6c0a07b67"
        }
      ],
      "title": "net: stmmac: fix integer underflow in chain mode",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31649",
    "datePublished": "2026-04-24T14:45:02.520Z",
    "dateReserved": "2026-03-09T15:48:24.128Z",
    "dateUpdated": "2026-04-24T14:45:02.520Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "cve": "CVE-2026-31649",
      "date": "2026-04-25",
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  }
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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