48 CFR 750.7106-3 - Mistakes.
A contract may be amended or modified to correct or mitigate the effect of a mistake, including the following examples:
(a) A mistake or ambiguity which consists of the failure to express or to express clearly in the written contract the agreements as both parties understood them;
(b) A mistake on the part of the contractor which is so obvious that it was or should have been apparent to the contracting officer; and
(c) A mutual mistake as to a material fact.