CVE-2025-21742

In the Linux kernel, the following vulnerability has been resolved:

usbnet: ipheth: use static NDP16 location in URB

Original code allowed for the start of NDP16 to be anywhere within the URB based on the wNdpIndex value in NTH16. Only the start position of NDP16 was checked, so it was possible for even the fixed-length part of NDP16 to extend past the end of URB, leading to an out-of-bounds read.

On iOS devices, the NDP16 header always directly follows NTH16. Rely on and check for this specific format.

This, along with NCM-specific minimal URB length check that already exists, will ensure that the fixed-length part of NDP16 plus a set amount of DPEs fit within the URB.

Note that this commit alone does not fully address the OoB read. The limit on the amount of DPEs needs to be enforced separately.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/2b619445dcb6dab97d8ed033fb57225aca1288c4
• https://git.kernel.org/stable/c/86586dcb75cb8fd062a518aca8ee667938b91efb
• https://git.kernel.org/stable/c/8fb062178e1ce180e2cfdc9abc83a1b9fea381ca
• https://git.kernel.org/stable/c/cf1ac7f7cf601ac31d1580559c002b5e37b733b7