Consider the specific case of random variables
$X\sim$ Bernoulli$\left(p\right)$,
$Y\sim$ Bernoulli$\left(q\right)$ and $X\oplus Y= X+Y \bmod 2$ being a Bernoulli$\left(r\right)$ random variable. Then, with $p_{ij}$ denoting
$P\{X=i,Y=j\} = p_{X,Y}(i,j)$, we have that
\begin{align}
p_{11} + p_{10} &= p\\
p_{11} + p_{01} &= q\\
p_{10} + p_{01} &= r
\end{align}
from which we can deduce that
\begin{alignat}{3} p_{00} &= 1 - (p_{11} + p_{10} +p_{01}) &&= 1 - \frac{p+q+r}{2}\\
p_{01} &= (1-p) - p_{00} = (1-p) - \left(1 - \frac{p+q+r}{2}\right)&&= \frac{q+r-p}{2}\\
p_{10} &= (1-q) - p_{00} = (1-q) - \left(1 - \frac{p+q+r}{2}\right) &&= \frac{p+r-q}{2}\\
p_{11} &= p - p_{10} = p - \frac{p+r-q}{2} &&=\frac{p-r+q}{2}\end{alignat}
It is, of course, to be hoped that the given value of $r$ is consistent
with the known values of $p$ and $q$ and that none of the joint mass function values calculated above turn out to be outside $[0,1]$.
The joint pmf of $m > 2$ Bernoulli random variables cannot be computed from knowledge of the parameters of a subset of the $2^m-1$ Bernoulli random variables $\displaystyle \sum_i a_iX_i \bmod 2, a_i \in \{0,1\}$.
For example, suppose that it is given that $X,Y,Z$ all are
Bernoulli$\left(\frac 12\right)$ random variables, and so
$X\oplus Y, X\oplus Z, Y\oplus Z$ all are Bernoulli$\left(\frac 12\right)$ random variables. (Note the absence of $X\oplus Y \oplus Z$ from the
list). Then, it is easily verified via calculations such
as the ones above that $X,Y,Z$ are pairwise independent random variables. But,
If $X,Y,Z$ are mutually independent random variables, then
$p_{111} = \frac 18$.
If $p_{000} = p_{110} = p_{101} = p_{011} = \frac 14$, then
$p_{111} = 0$.
If $p_{100} = p_{010} = p_{001} = p_{111} = \frac 14$, then
$p_{111} = \frac 14$.
In fact, for any given value $r \in [0,\frac 14]$ that $p_{111}$
might take on,
$p_{110} = p_{101} = p_{011} = \frac 14 -r$ from which we get that
$p_{100} + p_{101} = \frac 14 \implies p_{100} = r$ (and similarly
$p_{010}$ and $p_{001}$ also have value $r$ too) and finally that
$p_{000} = \frac 14 - r$. In short, the best bound that we can have for the $8$ pmf values $p_{ijk}$ is that they all are in $[0,\frac 14]$.
The reason for needing the parameters of all $2^m-1$ Bernoulli random variables $\displaystyle \sum_i a_iX_i \bmod 2, a_i \in \{0,1\}$ is easy to comprehend. Each such parameter gives us a linear equation involving $2^m-1$ joint pmf values ($p_{00\cdots 0}$ is not included anywhere), these equations are linearly independent (in the linear algebra sense
of the term), and so all are needed to find the unique solution for the joint pmf. If we don't have all the equations, then we get a parametrized
solution as in the example above.
