CVE-2024-41091

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

tun: add missing verification for short frame

The cited commit missed to check against the validity of the frame length in the tun_xdp_one() path, which could cause a corrupted skb to be sent downstack. Even before the skb is transmitted, the tun_xdp_one–>eth_type_trans() may access the Ethernet header although it can be less than ETH_HLEN. Once transmitted, this could either cause out-of-bound access beyond the actual length, or confuse the underlayer with incorrect or inconsistent header length in the skb metadata.

In the alternative path, tun_get_user() already prohibits short frame which has the length less than Ethernet header size from being transmitted for IFF_TAP.

This is to drop any frame shorter than the Ethernet header size just like how tun_get_user() does.

CVE: CVE-2024-41091

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/049584807f1d797fc3078b68035450a9769eb5c3
• https://git.kernel.org/stable/c/32b0aaba5dbc85816898167d9b5d45a22eae82e9
• https://git.kernel.org/stable/c/589382f50b4a5d90d16d8bc9dcbc0e927a3e39b2
• https://git.kernel.org/stable/c/6100e0237204890269e3f934acfc50d35fd6f319
• https://git.kernel.org/stable/c/8418f55302fa1d2eeb73e16e345167e545c598a5
• https://git.kernel.org/stable/c/a9d1c27e2ee3b0ea5d40c105d6e728fc114470bb
• https://git.kernel.org/stable/c/ad6b3f622ccfb4bfedfa53b6ebd91c3d1d04f146
• https://git.kernel.org/stable/c/d5ad89b7d01ed4e66fd04734fc63d6e78536692a
• https://git.kernel.org/stable/c/049584807f1d797fc3078b68035450a9769eb5c3
• https://git.kernel.org/stable/c/32b0aaba5dbc85816898167d9b5d45a22eae82e9
• https://git.kernel.org/stable/c/589382f50b4a5d90d16d8bc9dcbc0e927a3e39b2
• https://git.kernel.org/stable/c/6100e0237204890269e3f934acfc50d35fd6f319
• https://git.kernel.org/stable/c/8418f55302fa1d2eeb73e16e345167e545c598a5
• https://git.kernel.org/stable/c/a9d1c27e2ee3b0ea5d40c105d6e728fc114470bb
• https://git.kernel.org/stable/c/ad6b3f622ccfb4bfedfa53b6ebd91c3d1d04f146
• https://git.kernel.org/stable/c/d5ad89b7d01ed4e66fd04734fc63d6e78536692a
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html