CVE-2026-68453

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

s390/zcrypt: Fix buffer over-read in cca_cipher2protkey

Add validation of both the actual key buffer size and token length fields in all the cca_check_sec*token() functions. Additionally check in cca_gencipherkey() for possible underflow with returned key size.

The CCA token structures contain user-controlled len fields that were used in operations without proper validation against both the actual buffer size and minimum token structure size. An attacker could set this field larger than the actual buffer size, leading to reading beyond buffer boundaries. This may result in a kernel crash or exposure of memory via sending this as part of a request down to the crypto card. Also an attacker could have used a very small len value and thus enforce a buffer under-run which may produce similar effects as a over-read.

So now a key must

• key buf length must be at least sizeof the token struct
• the key len field inside the token must fit into the range of sizeof key token struct … key buf length

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/1adfec7be6f34c1073c9cf15040bc4e3fdc6dc51
• https://git.kernel.org/stable/c/353e442d18084b24fb3ede4e5adfca26b25f0e89
• https://git.kernel.org/stable/c/36b230835b8a008266aad22168ca52afacc8a58d
• https://git.kernel.org/stable/c/3b2abee2a678607ae27975bc6833785c2002df43
• https://git.kernel.org/stable/c/a57fd7fcdb63e2d5ceac78bbe825ec986062a9da
• https://git.kernel.org/stable/c/d0951ed366710a1a303b7cb2f8eb3d866cd68fc6