CVE-2026-64089

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

batman-adv: tt: fix negative lastchangesetlen

batadvpivtt::lastchangesetlen len was declared as s16, but the field is never intended to hold a negative value. When a value greater than 32767 is assigned, it wraps to a negative signed integer.

In batadvsendmyttresponse(), lastchangesetlen is temporarily widened to s32. The incorrectly negative s16 value propagates into the s32, causing batadvttpreparetvlvlocal_data() to allocate a full sized buffer but populates only a small portion of it with the collected changeset. All remaining bits are kept uninitialized.

Using an u16 avoids this type confusion and ensures that no (negative) sign extension is performed in batadvsendmyttresponse().