mouse07410/asn1c is an ASN.1 compiler. Prior to 1.2.5, "OPEN TYPE" decoding can dereference an unallocated member pointer and crash the consuming program. "OPEN_TYPE_aper_get" in "OPEN_TYPE_aper.c", "OPEN_TYPE_ber_get" in "OPEN_TYPE_ber.c", "OPEN_TYPE_oer_get" in "OPEN_TYPE_oer.c", and "OPEN_TYPE_uper_get" in "OPEN_TYPE_uper.c" share the pattern: a conditional null check on "*memb_ptr2" resets presence only when the member exists, but execution then unconditionally computes an inner value from that pointer and a member offset. If the "OPEN TYPE" member has not been allocated, the null-pointer arithmetic and subsequent read cause a segmentation fault. The advisory demonstrates UPER and APER crashes for "E2connectionUpdateAcknowledge", notes that "E2AP" uses APER, and provides a BER reproducer; OER is also explicitly identified as affected. This issue is fixed in version 1.2.5.