CVE-2026-31435

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

netfs: Fix read abandonment during retry

Under certain circumstances, all the remaining subrequests from a read request will get abandoned during retry. The abandonment process expects the subreq variable to be set to the place to start abandonment from, but it doesnt always have a useful value (it will be uninitialised on the first pass through the loop and it may point to a deleted subrequest on later passes).

Fix the first jump to abandon: to set subreq to the start of the first subrequest expected to need retry (which, in this abandonment case, turned out unexpectedly to no longer have NEED_RETRY set).

Also clear the subreq pointer after discarding superfluous retryable subrequests to cause an oops if we do try to access 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/3e5fd8f53b575ff2188f82071da19c977ca56c41
• https://git.kernel.org/stable/c/7e57523490cd2efb52b1ea97f2e0a74c0fb634cd
• https://git.kernel.org/stable/c/8f2f2bd128a8d9edbc1e785760da54ada3df69b7