CVE-2026-31464

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

scsi: ibmvfc: Fix OOB access in ibmvfc_discover_targets_done()

A malicious or compromised VIO server can return a num_written value in the discover targets MAD response that exceeds max_targets. This value is stored directly in vhost->num_targets without validation, and is then used as the loop bound in ibmvfc_alloc_targets() to index into disc_buf[], which is only allocated for max_targets entries. Indices at or beyond max_targets access kernel memory outside the DMA-coherent allocation. The out-of-bounds data is subsequently embedded in Implicit Logout and PLOGI MADs that are sent back to the VIO server, leaking kernel memory.

Fix by clamping num_written to max_targets before storing it.

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/394a1cac3c12fdd7d77f19ccfd222ab5ff87ef89
• https://git.kernel.org/stable/c/4ed727e35b0ab17d3eeeb1e8023768396e2be161
• https://git.kernel.org/stable/c/61d099ac4a7a8fb11ebdb6e2ec8d77f38e77362f
• https://git.kernel.org/stable/c/786f10b1966e485046839f992e89f2c18cbd1983
• https://git.kernel.org/stable/c/a007246cb6c9ebdc93dafbf63cc2d43d98f402cc
• https://git.kernel.org/stable/c/bae4df0a643fa7f84663473aa3082a9c2ed139db
• https://git.kernel.org/stable/c/d1466bf991b2343cf2ba8336e440c8faf3cbb780
• https://git.kernel.org/stable/c/d842348f8a00d5b1d7358f207eb34ffcf5b16df3