CVE-2026-63912

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

xfrm: esp: restore combined single-frag length gate

The ESP out-of-place fast path appends the trailer in esp_output_head() before esp_output_tail() allocates the destination page frag. The head-side gate currently checks skb->data_len and tailen separately, but the tail code allocates a single destination frag from the combined post-trailer skb->data_len.

Reject the page-frag fast path when the combined aligned length exceeds a page. Otherwise skb_page_frag_refill() may fall back to a single page while the destination sg still spans the combined skb->data_len.

Restore this combined-length page gate for both IPv4 and IPv6.

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/322e48187e0245ab2fff6fec2220b0cae677dbec
• https://git.kernel.org/stable/c/36519e3d941fc99d3b52c134dbaf311f987a4708
• https://git.kernel.org/stable/c/566295735530ee513326049b0540f32ec050bf2e
• https://git.kernel.org/stable/c/5d7ab86e2b6bc23054616bf6ac562013bf60af8c
• https://git.kernel.org/stable/c/65f3b3fc2347b89fe21db1e92c7681368415f095
• https://git.kernel.org/stable/c/b84091ceddc9f133229dceab3ccc930bf27f9cba
• https://git.kernel.org/stable/c/c093468aea8277f77272a4f199b2e15e19cabb59
• https://git.kernel.org/stable/c/dfa0d7b0ff1eb6b2c416b8fdb9b4f2cefba57a40