ghsa-6p7j-vrw4-43wh
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow
Sending an PF_PACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PF_PACKET framework is to make sure that skb->len fits the interface's MTU.
Unfortunately, because the sun4i_can driver does not populate its net_device_ops->ndo_change_mtu(), it is possible for an attacker to configure an invalid MTU by doing, for example:
$ ip link set can0 mtu 9999
After doing so, the attacker could open a PF_PACKET socket using the ETH_P_CANXL protocol:
socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))
to inject a malicious CAN XL frames. For example:
struct canxl_frame frame = {
.flags = 0xff,
.len = 2048,
};
The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks:
-
the skb->protocol is set to ETH_P_CANXL which is valid (the function does not check the actual device capabilities).
-
the length is a valid CAN XL length.
And so, sun4ican_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame.
This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on this line:
dlc = cf->len;
Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs a couple line below when doing:
for (i = 0; i < dlc; i++)
writel(cf->data[i], priv->base + (dreg + i * 4));
Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU. By fixing the root cause, this prevents the buffer overflow.
{
"affected": [],
"aliases": [
"CVE-2025-39986"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-15T08:15:36Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow\n\nSending an PF_PACKET allows to bypass the CAN framework logic and to\ndirectly reach the xmit() function of a CAN driver. The only check\nwhich is performed by the PF_PACKET framework is to make sure that\nskb-\u003elen fits the interface\u0027s MTU.\n\nUnfortunately, because the sun4i_can driver does not populate its\nnet_device_ops-\u003endo_change_mtu(), it is possible for an attacker to\nconfigure an invalid MTU by doing, for example:\n\n $ ip link set can0 mtu 9999\n\nAfter doing so, the attacker could open a PF_PACKET socket using the\nETH_P_CANXL protocol:\n\n\tsocket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL))\n\nto inject a malicious CAN XL frames. For example:\n\n\tstruct canxl_frame frame = {\n\t\t.flags = 0xff,\n\t\t.len = 2048,\n\t};\n\nThe CAN drivers\u0027 xmit() function are calling can_dev_dropped_skb() to\ncheck that the skb is valid, unfortunately under above conditions, the\nmalicious packet is able to go through can_dev_dropped_skb() checks:\n\n 1. the skb-\u003eprotocol is set to ETH_P_CANXL which is valid (the\n function does not check the actual device capabilities).\n\n 2. the length is a valid CAN XL length.\n\nAnd so, sun4ican_start_xmit() receives a CAN XL frame which it is not\nable to correctly handle and will thus misinterpret it as a CAN frame.\n\nThis can result in a buffer overflow. The driver will consume cf-\u003elen\nas-is with no further checks on this line:\n\n\tdlc = cf-\u003elen;\n\nHere, cf-\u003elen corresponds to the flags field of the CAN XL frame. In\nour previous example, we set canxl_frame-\u003eflags to 0xff. Because the\nmaximum expected length is 8, a buffer overflow of 247 bytes occurs a\ncouple line below when doing:\n\n\tfor (i = 0; i \u003c dlc; i++)\n\t\twritel(cf-\u003edata[i], priv-\u003ebase + (dreg + i * 4));\n\nPopulate net_device_ops-\u003endo_change_mtu() to ensure that the\ninterface\u0027s MTU can not be set to anything bigger than CAN_MTU. By\nfixing the root cause, this prevents the buffer overflow.",
"id": "GHSA-6p7j-vrw4-43wh",
"modified": "2025-10-15T09:30:17Z",
"published": "2025-10-15T09:30:17Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39986"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/063539db42203b29d5aa2adf0cae3d68c646a6b6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2e423e1990f3972cbea779883fef52c2f2acb858"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4f382cc887adca8478b9d3e6b81aa6698a95fff4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/60463a1c138900494cb3adae41142a11cd8feb3c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/61da0bd4102c459823fbe6b8b43b01fb6ace4a22"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7f7b21026a6febdb749f6f6f950427245aa86cce"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a61ff7ac93270d20ca426c027d6d01c8ac8e904c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de77841652e57afbc46e9e1dbf51ee364fc008e1"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
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